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North America Land Data Assimilation System (NLDAS)
Daily Air Temperatures and Heat Index
1979 - 2010

Summary

The North America Land Data Assimilation System (NLDAS) data available on CDC WONDER are county-level daily average air temperatures and heat index measures spanning the years 1979-2010. Temperature data are available in Fahrenheit or Celsius. Reported measures are the average temperature, number of observations, and range for the daily maximum and minimum air temperatures, and the daily maximum heat index. The Percent Coverage measure is also available for the daily maximum heat index. Data are available by place (combined 48 contiguous states plus the District of Columbia, region, division, state, county), time (year, month, day) and specified maximum and minimum air temperature, and maximum heat index value.

Source:

NLDAS Phase 2 is a collaboration project among several groups:  the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Prediction (NCEP) Environmental Modeling Center (EMC), the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), Princeton University, the National Weather Service (NWS) Office of Hydrological Development (OHD), the University of Washington, and the NCEP Climate Prediction Center (CPC). The NLDAS Phase 2 (NLDAS-2) hourly forcing data used in this study were acquired as part of the mission of the NASA Earth Science Division. NLDAS-2 data are archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC). More information about the NLDAS project and raw data can be found at ftp://hydro1.sci.gsfc.nasa.gov/data/s4pa/NLDAS/README.NLDAS2.pdf.

In a study funded by the NASA Applied Sciences Program/Public Health Program (fully cited below), scientists at NASA Marshall Space Flight Center/ Universities Space Research Association developed computer programs to process the NLDAS-2 hourly primary forcing files, extract the hourly air temperature, specific humidity, and atmospheric pressure data, and compute the daily Maximum Air Temperature, Minimum Air Temperature, and Maximum Heat Index. They also identified in a Geographic Information System (GIS) the associated geographic locations of the centroids of the gridded NLDAS-2 dataset in terms of the counties and states they fall into so it can be aggregated to different geographic levels in CDC WONDER.

See also Data Source Information.

In WONDER: You can produce tables, maps, charts, and data extracts. Obtain average temperature, the number of observations, range, and percent coverage (percent coverage available for daily maximum heat index only). Select specific criteria to produce cross-tabulated average air temperature and heat index measures. Data are organized into three levels of geographic detail: the 48 contiguous states, state (including multi-state regions and divisions) and county. You can limit and index your data by any and all of the variables.
Contents: NLDAS Data Request
Data Source Information
Additional Information

NLDAS Data Request

Output You can produce tables, maps, charts, and data extracts. Obtain average temperature, the number of observations, range, and percent coverage (percent coverage available for daily maximum heat index only). Select specific criteria to produce cross-tabulated average air temperature and heat index measures. Data are organized into three levels of geographic detail: the 48 contiguous states, state (including multi-state regions and divisions) and county. You can limit and index your data by any and all of the variables.
Variables You can limit and index your data by any and all of these variables:
  1. Location: Region, Division, State, County
  2. Year 1979-2010
  3. Month January - December, available also as specific "Month, Year" values
  4. Day Available as specific "Month Day, Year" values, or as Day of Month (1-31) or as Day of Year (1-366)
  5. Daily Maximum Air Temperature -26 through 124 degrees Fahrenheit, or -32 through 51 degrees Celsius
  6. Daily Minimum Air Temperature -39 through 100 degrees Fahrenheit, or -39 through 38 degrees Celsius
  7. Daily Maximum Heat Index 78 through 125 degrees Fahrenheit, and Not Applicable, or 25 through 52 degrees Celsius, and Not Applicable
How? The Request screen has sections to guide you through the making a data request as step-by-step process. However, to get your first taste of how the system works, you might want to simply press any Send button, and execute the default data request. The data results for your query appear on the Table screen. After you get your data results, try the Chart and Map screens. Or export your data to a file (tab-delimited line listing) for download to your computer.
For more information, see the Quick Start Guide and the following steps:
  1. Organize table layout
  2. Select location
  3. Select year, month, day
  4. Select values for temperature
  5. Other options
'By-Variables' Select variables that serve as keys (indexes) for organizing your data. See "How do I organize my data?" for more information.
Note:   To map your data, you must select at least one geographical location as a "By-Variable" for grouping your data, such as State or County.
Help Click on any button labeled "Help", located to the right hand side of the screen at the top of each section. Each control's label, such as the "Location" label next to the Location entry box, is linked to the on-line help for that item.
Send Sends your data request to be processed on the CDC WONDER databases. The Send buttons are located on the bottom of the Request page, and also in the upper right corner of each section, for easy access.

Step 1. Organize table layout:
Group Results By   Select up to five variables that serve as keys for grouping your data. See Group Results By below for hints.
Select Temperature Scale   Choose either Fahrenheit or Celsius scale. Click the round radio button to indicate your choice.
Select Measures   If checked, these measures will appear in the results table. You must select at least one measure: 
  1. Average temperature of the temperature measurements that met the criteria for this cell
  2. Number of observations, how many measurements went into this summary statistic
  3. Range or minimum - maximum value for this summary statistic
  4. Percent Coverage (for Daily Maximum Heat Index only)
The four summary measures above are available for these three items:
  1. Daily Maximum Air Temperature
  2. Daily Minimum Air Temperature
  3. Daily Maximum Heat Index
Title   Enter any desired description to display as a title with your results.
Group Results By...

Select up to five variables that serve as keys for grouping your data. For example, you could select to group (summarize, stratify, index) your data by State and by County.

How?    See "How do I organize my data?" for more information.

Hints:   

  1. About charts:
    You cannot make charts when your data has more than two By-Variables.
  2. About maps:
    To make a map, you must request data with a geographic location variable, such as Region, as the first "By-Variable" in the "Group Results By" box. Send your data request, then click the Map tab when you get the results.
Average Temperature

The average temperature summary measure is the mean value of all of the daily temperature measurements that met the criteria for this cell in the results table. For example, if results are grouped by Year and limited to the South Region for years 1979-2010, then the first row shows the value 70.82 (F) or 21.57 (C) as the mean daily maximum air temperature for year 1979 in the South Region. This summary measure is the mean of the daily values recorded for daily maximum air temperature measurements of the 1/8-degree (14x14 kilometer square) geographic-area grids in the selected time and place.

How?
  1. First select your preferred temperature scale using the round radio button in section 1. Organize table layout on the Request Form.
  2. Then select the checkbox labeled "Avg Temperature" under the desired measurement in the "Select Measures" heading in section 1. Organize table layout on the Request Form.

Notes:
  • The average temperature summary measurement is the mean value of all of the daily temperature measurements that met the selected criteria for time and place.
  • This dataset contains daily air temperature measurements, an average air temperature measurement (for each of three measures: maximum air temperature, minimum air temperature and maximum heat index when applicable) per day per geographic-area (14x14 kilometer square) grid covering the 48 contiguous United states (not including Alaska and Hawaii) plus the District of Columbia.
  • NLDAS temperature measurements are recorded for 1/8-degree (14x14 kilometer square) geographic-area grids in the selected area. Temperature measurements from each grid are assigned to the county where the grid centroid is located. Some counties are so small that no centroids are located in the county; temperature measurements from the grid that covers the greatest county area are assigned to such counties. WONDER aggregates the grid-level measurements into counties and larger areas. The county locations are from the 1999-2000 Federal Information Processing (FIPS) code set.
  • Note that maximum heat index data are sparse. Heat index data are recorded only for days when the air temperature is above 80 degrees Fahrenheit (26.7 degrees Celsius). See Additional Information for more information about heat index data.

Number of Observations

The number of observations is the number of daily air temperature measurements that produced the summary measure. For example, for January 1, 2008, there were 52,314 air temperature measurements averaged to produce the national average daily maximum air temperature value of 32.52 degrees Fahrenheit, and the national average daily minimum air temperature value of 18.14 degrees Fahrenheit. The observations are the daily air temperature values recorded for the 1/8-degree (14x14 kilometer square) geographic-area grids in the selected time and place.

How?
  1. First select your preferred temperature scale using the round radio button in section 1. Organize table layout on the Request Form.
  2. Then select the checkbox labeled "# of Observations" under the desired measurement in the "Select Measures" heading in section 1. Organize table layout on the Request Form.

Notes:
  • The number of observations is the total number of daily air temperature values recorded for the 1/8-degree (14x14 kilometer square) geographic-area grids in the selected time and place.
  • This dataset contains daily air temperature measurements, an average air temperature measurement (for each of three measures: maximum air temperature, minimum air temperature and maximum heat index when applicable) per day per geographic-area (14x14 kilometer square) grid covering the 48 contiguous United states (not including Alaska and Hawaii) plus District of Columbia.
  • NLDAS temperature measurements are recorded for 1/8-degree (14x14 kilometer square) geographic-area grids in the selected area. Temperature measurements from each grid are assigned to the county where the grid centroid is located. Some counties are so small that no centroids are located in the county; temperature measurements from the grid that covers the greatest county area are assigned to such counties. WONDER aggregates the grid-level measurements into counties and larger areas. The county locations are from the 1999-2000 Federal Information Processing (FIPS) code set.
  • Note that maximum heat index data are sparse. Heat index data are recorded only for days when the air temperature is above 80 degrees Fahrenheit (26.7 degrees Celsius). See Additional Information for more information about heat index data.

Range

The range shows the minimum and maximum air temperature measurement for the criteria that defines the cell in the table, from all of the grid-level observations that contribute to the spatial average daily measurement. For example, when data are grouped by year and limited to the District of Columbia in year 2008, for the 366 observations of Average Daily Minimum Air Temperature, the lowest minimum air temperature was 12.5 degrees Fahrenheit and the highest minimum air temperature was 75.3 degrees Fahrenheit.

How?
  1. First select your preferred temperature scale using the round radio button in section 1. Organize table layout on the Request Form.
  2. Then select the checkbox labeled "Range" under the desired measurement in the "Select Measures" heading in section 1. Organize table layout on the Request Form.

Notes:
  • The range shows the lowest and the highest air temperature values in the set that defines the average air temperature measurement in the table cell, in the format: (minimum - maximum). Daily air temperature values are recorded for the 1/8-degree (14x14 kilometer square) geographic-area grids in the selected time and place.
  • Note that the categorical values for temperature reflect the rounded average temperature measurement values, and vary from the actual range of recorded grid-level temperature observations. For example, if data are grouped by Daily Minimum Air Temperature, and limited to the District of Columbia in year 2008, then the categorical value 37 degrees Fahrenheit maps to the calculated Average Daily Minimum Air Temperature measure of 36.96 degrees Fahrenheit, based on a range of actual recorded Daily Minimum Air Temperature values of (36.50 to 37.40) for the 1/8-degree (14x14 kilometer square) geographic-area grids.
  • This dataset contains daily air temperature measurements, an average air temperature measurement (for each of three measures: maximum air temperature, minimum air temperature and maximum heat index when applicable) per day per geographic-area (14x14 kilometer square) grid covering the 48 contiguous United states (not including Alaska and Hawaii) plus District of Columbia.
  • NLDAS temperature measurements are recorded for 1/8-degree (14x14 kilometer square) geographic-area grids in the selected area. Temperature measurements from each grid are assigned to the county where the grid centroid is located. Some counties are so small that no centroids are located in the county; temperature measurements from the grid that covers the greatest county area are assigned to such counties. WONDER aggregates the grid-level measurements into counties and larger areas. The county locations are from the 1999-2000 Federal Information Processing (FIPS) code set.
  • Note that maximum heat index data are sparse. Heat index data are recorded only for days when the air temperature is above 80 degrees Fahrenheit (26.7 degrees Celsius). See Additional Information for more information about heat index data.

Percent Coverage

The percent coverage measure reports the coverage of Daily Maximum Heat Index grid-level observations for the selected time and place reported in the table cell. For example, for the District of Columbia in year 1979, for the 67 observations of daily maximum heat index, which ranged from 81.6 - 102.2 degrees Fahrenheit, the percent coverage of daily maximum heat index values for this location was 18.36%.

How?
  1. First select your preferred temperature scale using the round radio button in section 1. Organize table layout on the Request Form.
  2. Then select the checkbox labeled "Percent Coverage" under the desired measurement in the "Select Measures" heading in section 1. Organize table layout on the Request Form.

Notes:
  • The percent coverage measure reports the coverage of Daily Maximum Heat Index grid-level observations for the selected time and place reported in the table cell.
  • Note that maximum heat index data are sparse. Heat index data are recorded only for days when the air temperature is above 80 degrees Fahrenheit (26.7 degrees Celsius). See Additional Information for more information about heat index data.

Step 2. Select location:

Select the place of interest:
  1. Location:   the 48 contiguous United States plus District of Columbia by Region, Division, State, and County

Location

Data are available for the United States by Region, Division, State, County. Select the location(s) for the query. Any number of locations can be specified here.

How? Hints:
  • The default is all values (the United States).
  • The Advanced mode let you easily pick several items from different parts of the list. Items are not selected until you click the "Move" button in Advanced mode. You may also enter values by hand, one code per line, in the Advanced mode. Use the Finder to see the correct code format. For example, 02 is the Alaska state code.
  • The "plus" symbol, "+" indicates that you can open the item, to see more items below it.
  • The results to a search are shown in blue, and indicated by ">".

Region

Regions are multi-state groups. For regional data, you can group by Region, or you can select any combination of individual regions.
How?   Notes:  
  • The Regions are identified by both name and codes in data extracts.
  • The United States is split into 4 regions: Northeast, Midwest, South and West. The states that comprise each region are shown below. 

State abbreviation and name   FIPS code
________________________________________
Northeast Region: 
CT    Connecticut               09
ME    Maine                     23
MA    Massachusetts             25
NH    New Hampshire             33
NJ    New Jersey                34
NY    New York                  36
PA    Pennsylvania              42
RI    Rhode Island              44
VT    Vermont                   50
________________________________________
Midwest Region: 
IL    Illinois                  17
IN    Indiana                   18
IA    Iowa                      19
KS    Kansas                    20
MI    Michigan                  26
MN    Minnesota                 27
MO    Missouri                  29
NE    Nebraska                  31
ND    North Dakota              38
OH    Ohio                      39
SD    South Dakota              46
WI    Wisconsin                 55
________________________________________
South Region: 
AL    Alabama                   01
AR    Arkansas                  05
DE    Delaware                  10
DC    District of Columbia      11
FL    Florida                   12
GA    Georgia                   13
KY    Kentucky                  21
LA    Louisiana                 22
MD    Maryland                  24
MS    Mississippi               28
NC    North Carolina            37
OK    Oklahoma                  40
SC    South Carolina            45
TN    Tennessee                 47
TX    Texas                     48
VA    Virginia                  51
WV    West Virginia             54
________________________________________
West Region: 
AK    Alaska *                 02
AZ    Arizona                  04
CA    California               06
CO    Colorado                 08
HI    Hawaii *                 15
ID    Idaho                    16
MT    Montana                  30
NV    Nevada                   32
NM    New Mexico               35
OR    Oregon                   41
UT    Utah                     49
WA    Washington               53
WY    Wyoming                  56
________________________________________ 

 * Alaska and Hawaii are not included in these data.

Division

Divisions are multi-state groups, sub-sets of Regions. For division-level data, you can group by Division, or select any combination of individual divisions.
How?   Notes:  

State

For state level data, you can select any combination of individual states. Or group by State and leave the Location Finder selection at the default (all locations or the 48 United States and the District of Columbia).
How?   Notes:  
  • The states and the District of Columbia are identified by both state name and Standard Federal Information Processing (FIPS) codes in data extracts. See About FIPS Codes below.

County

County-level data are available for the United States and the District of Columbia. For county level data, you can select any combination of individual counties, or group by County. Leave the Location Finder selection at the default (all locations or the 48 United States and the District of Columbia).
How?   Notes:  
  • The county coded represents the spatial average of data observations from 14x14 kilometer square (1/8 degree) geographic-area grids. Grids are coded to the county that includes the grid centroid. For small counties where no grid centroid fell within county boundaries, county data are aggregated from grids where most of the grid area fell within county boundaries.
  • The counties and the District of Columbia are identified by both county name and Standard Federal Information Processing (FIPS) codes in data extracts. The county locations are from the 1999-2000 Federal Information Processing (FIPS) code set.
  • About FIPS Codes:   The FIPS State and county codes were established by the National Bureau of Standards, U.S. Department of Commerce in 1968. This standard set of codes provides names and codes for counties and county equivalents of the 50 States of the United States and the District of Columbia. Counties are considered to be the "first order subdivisions" of each State, regardless of their local designation (county, parish, borough, census area). Washington, D.C.; the consolidated government of Columbus City, Georgia; the independent cities of the States of Maryland, Missouri, Nevada, and Virginia; and the census areas and boroughs of Alaska are identified as county equivalents. The system is standard throughout the Federal Government. The State codes are ascending, two-digit numbers; the county codes are ascending three-digit numbers. For both the State and county codes, space has been left for new States or counties. Some changes in the FIPS codes and county boundaries have occurred since 1968. See Location Updates for information on how these changes affect the data.
  • About County Changes:   Comparable measures may be misleading for counties with changing boundaries. See Location Updates for information on how these changes affect the data. Due to boundary changes, data are available for some counties for a limited period of time.
    The following county-level constraints apply to the data:
    • Alaska: data for Alaska are not included in this NLDAS average daily air temperature collection.
    • Colorado:
    • Florida:
      • Dade county, Florida (FIPS code 12025) - data are shown for the Dade county code value 12025, also the location of Miami, Florida.
    • Hawaii: data for Hawaii are not included in this NLDAS average daily air temperature collection.

Step 3. Select year, month and day:
Select the time period for the query. Any number of dates can be specified here. Individual date fields allow you to separately limit or filter data for Year (1979-2010), Month (January - December), and Day of Month (1-31) or Day of Year (1-366). The Aggregate Date Finder lets you select specific year/month/day dates, such as January 1, 1979.
How? Hints for the Aggregate Date Finder:
  • The default for the Aggregate Date Finder is all values (1979/01/01 - 2010/12/31).
  • The Advanced mode let you easily pick several items from different parts of the list. Items are not selected until you click the "Move" button in Advanced mode. You may also enter values by hand, one code per line, in the Advanced mode. The code format is YYYY/MM/DD. For example, 2003/09/01 is September 1, 2003.
  • The "plus" symbol, "+" indicates that you can open the item, to see more items below it.
  • The results to a search are shown in blue, and indicated by ">".

Year

Select All Years or any number of individual years (1979 - 2010).
How?  
  • Click a round button to indicate Individual Date Fields.
  • Click your left Mouse button on any desired single option in the list box.
  • Press the Ctrl key while clicking your left Mouse button to make multiple selections.
  • Press the Shift key while clicking your left Mouse button and dragging the selection for a range of values.

Month

Select All Months or any number of individual months (January - December).
How?  
  • Click a round button to indicate Individual Date Fields.
  • Click a round button to indicate Day of Month Fields.
  • Click your left Mouse button on any desired single option in the list box.
  • Press the Ctrl key while clicking your left Mouse button to make multiple selections.
  • Press the Shift key while clicking your left Mouse button and dragging the selection for a range of values.

Day of Month

Select All Days or any number of individual days (1 - 31).
How?  
  • Click a round button to indicate Individual Date Fields.
  • Click a round button to indicate Day of Month Fields.
  • Click your left Mouse button on any desired single option in the list box.
  • Press the Ctrl key while clicking your left Mouse button to make multiple selections.
  • Press the Shift key while clicking your left Mouse button and dragging the selection for a range of values.
Notes:  
Data are reported as "Missing" when the selections in the Individual Date Fields are not found in the data. For example, if data are limited to Day of Month values (29, 30, 31) for All Years in the month of February, then data are only reported for February 29 in year 2004 and year 2008. If the query also shows the data grouped by "Day of Month" and shows zero-value rows, then you see "Missing" in the cells for days 30 and 31.

Step 4. Select temperature values:
Limit your data for any of the following data elements:
  1. Daily Max Air Temperature - All Temperatures, -26 - 124 (F) or -32 - 51 (C)
  2. Daily Min Air Temperature - All Temperatures, -39 - 100 (F) or -39 - 38 (C)
  3. Daily Max Heat Index - All Heat Index values, 78 - 125 (F) or 25 - 52 (C), Not Applicable
How?  
  • Click a round button to indicate Fahrenheit or Celsius temperature scales, in Section 1.
  • Click your left Mouse button on any desired single option in the list box.
  • Press the Ctrl key while clicking your left Mouse button to make multiple selections.
  • Press the Shift key while clicking your left Mouse button and dragging the selection for a range of values.

Daily Max Air Temperature

Limit your data to the selected daily maximum air temperature values. First click the round radio button to show the preferred temperature scale in Section 1. Then select All Temperatures or any combination of the individual values in the list box.

How?  

Notes:  

  • Note that the values in the list box are the range of average values available in the data. These categorical values are based on the rounded average values. For example, an average value from "1.5" to "2.4" is categorized as "2".
  • Values are a spatial average of the daily maximum air temperatures recorded for each 14x14 kilometer square grid, aggregated at the county level.

Daily Min Air Temperature

Limit your data to the selected daily minimum air temperature values. First click the round radio button to show the preferred temperature scale in Section 1. Then select All Temperatures or any combination of the individual values in the list box.

How?  

Notes:  

  • Note that the values in the list box are the range of average values available in the data. These categorical values are based on the rounded average values. For example, an average value from "1.5" to "2.4" is categorized as "2".
  • Values are a spatial average of the daily minimum air temperatures recorded for each 14x14 kilometer square grid, aggregated at the county level.

Daily Max Heat Index

Limit your data to the selected daily maximum heat index values. First click the round radio button to show the preferred temperature scale in Section 1. Then select All Temperatures or any combination of the individual values in the list box.

How?  

Notes:  

  • Note that the values in the list box are the range of average values available in the data. These categorical values are based on the rounded average values. for example, an average value from "1.5" to "2.4" is categorized as "2".
  • Values are a spatial average of the daily maximum heat index values recorded for each 14x14 kilometer square grid, aggregated at the county level.
  • Note that maximum heat index data are sparse. Heat index data are recorded only for days when the air temperature is above 80 degrees Fahrenheit (26.7 degrees Celsius). See Additional Information for more information about heat index data.

Step 5. Other options:
Export Results   If checked query results are exported to a local file. More information on how to import this file into other applications can be found here.
How? See "How do I use a checkbox?"
Show Totals   If checked totals and sub-totals will appear in the results table.
How? See "How do I use a checkbox?"
Show Zero Values   If checked, rows containing zero counts are included in the results table. If unchecked, zero count rows are not included.
How? See "How do I use a checkbox?"
Precision   Select the precision for rate calculations. When the rate calculated for a small numerator (incidence count) is zero, you may increase the precision to reveal the rate by showing more numbers to the right of the decimal point.
How? See "How do I select items from the list box?"
Data Access Timeout   This value specifies the maximum time to wait for the data access for a query to complete. If the data access takes too long to complete, a message will be displayed and you can increase the timeout or simplify your request. If you can't complete a request using the maximum timeout, contact user support and we will try to run a custom data request for you.
How? See "How do I select items from the list box?"

Data Source Information

Data Sources NLDAS Phase 2 is a collaboration project among several groups:  the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Prediction (NCEP) Environmental Modeling Center (EMC), the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), Princeton University, the National Weather Service (NWS) Office of Hydrological Development (OHD), the University of Washington, and the NCEP Climate Prediction Center (CPC). The NLDAS Phase 2 (NLDAS-2) hourly forcing data used in this study were acquired as part of the mission of NASA's Earth Science Division and archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC).

In a study funded by the NASA Applied Sciences Program/Public Health Program (fully cited below), scientists at NASA Marshall Space Flight Center /Universities Space Research Association developed computer programs to process the NLDAS-2 hourly primary forcing files, extract the hourly air temperature, specific humidity, and atmospheric pressure data, and compute the daily Maximum Air Temperature, Minimum Air Temperature, and Maximum Heat Index. They also identified in a Geographic Information System (GIS) the associated geographic locations of the centroids of the gridded NLDAS-2 dataset in terms of the counties and states they fall into.

To learn more about the methods and source of the NLDAS-2 data, please reference:

Additional Information

Suggested Data Source Citations

North America Land Data Assimilation System (NLDAS) Daily Air Temperatures and Heat Index, years 1979-2010 on CDC WONDER Online Database, released 2012.

The suggested citation including the original series for the data is shown below each table, chart or map.

Contact For data questions that are not addressed in this document, e-mail mohammad.alhamdan@nasa.gov or bill.crosson@nasa.gov
Acknowledgements This work was part of a collaborative study funded by the NASA Applied Sciences Program/Public Health Program (grant# NNX09AV81G), whose team members are:
  • Dr. Leslie McClure (PI), School of Public Health, University of Alabama at Birmingham
  • Dr. Mohammad Al-Hamdan (Co-PI), Universities Space Research Association, NASA Marshall Space Flight Center
  • Dr. William Crosson (Co-I), Universities Space Research Association, NASA Marshall Space Flight Center
  • Ms. Sigrid Economou (Collaborator), National Center for Public Health Informatics, Centers for Disease Control and Prevention
  • Mr. Maurice Estes, Jr. (Co-I), Universities Space Research Association, NASA Marshall Space Flight Center
  • Ms. Sue Estes (Co-I), Universities Space Research Association, NASA Marshall Space Flight Center
  • Mr. Mark Puckett (Collaborator), National Center for Public Health Informatics, Centers for Disease Control and Prevention
  • Dr. Dale Quattrochi, Jr. (Co-I), Earth Science Office, NASA Marshall Space Flight Center
Other Topics: Reference the following topics:
About Heat Index Methodology
Locations: About County Level Changes
Contact for Data Questions
Suggested Citation



About Heat Index Methodology

Heat Index data are available for days with temperatures at or above 80 degrees Fahrenheit or 26.7 degrees Celsius.

This formula was used to calculate the hourly Heat Index, from which the daily maximum Heat Index was computed:

HI = -42.379 + 2.04901523*T + 10.14333127*RH - 0.22475541*T*RH - 0.00683783*T2 - 0.05481717*RH2 + 0.00122874*T2*RH + 0.00085282*T*RH2 - 0.00000199*T2*RH2

where

HI = heat index (in degrees Fahrenheit)
T = ambient dry bulb temperature (in degrees Fahrenheit)
RH = relative humidity (integer percentage)

The formula above is a multiple regression equation fit to the original table of theoretical values published in Steadman, R.G., 1979: The assessment of sultriness. Part I: A temperature-humidity index based on human physiology and clothing science. J. Appl. Meteor., 18, 861-873.

The equation originates from: Lans P. Rothfusz. "The Heat Index 'Equation' (or, More Than You Ever Wanted to Know About Heat Index)", Scientific Services Division (NWS Southern Region Headquarters), 1 July 1990.

Location Updates: notes about specific county-level changes in boundaries and codes

Comparable measures may be misleading for counties with changing boundaries. The data collection may lag behind some Federal Information Processing (FIPS) location code changes. Some places, such as independent cities and New York City boroughs are included as unique locations in the data. Some county and census tract area (CA) locations are not included, instead the data are associated with a neighboring county or the previous location name and FIPS code. The list below of county-level changes is organized alphabetically by state name and then county name.

  1. Alaska boroughs and census areas:
    Data are not available for the state of Alaska, nor Alaskan boroughs and census areas.
  2. Colorado: Broomfield county
    Broomfield county, Colorado (FIPS code 08014) was created effective November 15, 2001 from parts of four counties: Adams, Boulder, Jefferson, and Weld. Data are not available for Broomfield county. Data are aggregated within the previous boundaries of adjacent Adams, Boulder, Jefferson, and Weld counties.
  3. Florida: Dade county and Miami city
    Dade county, Florida (FIPS code 12025) was renamed Miami-Dade County and its FIPS code changed to 12086, effective November 13, 1997. The previous label and code, Dade county (FIPS code 12025), are used here.
  4. Maryland: Baltimore city and Baltimore county
    The independent city of Baltimore, Maryland has been treated as a county. Data are reported separately for Baltimore city (FIPS code 24510) and Baltimore county (FIPS code 24005).
  5. Missouri:
    1. St. Genevieve county, Missouri
      In order to achieve alphabetical consistency, the FIPS code for St. Genevieve, Missouri was changed in 1979 from 29193 to 29186. The new code (29186) is used here.
    2. St. Louis city and St. Louis county, Missouri
      The independent city of St. Louis, Missouri has been treated as a county. Data are reported separately for St. Louis city (FIPS code 29510) and St. Louis county (FIPS code 29189).
  6. Nevada: Carson City
    The independent city of Carson City, Nevada (FIPS code 32510) has been treated as a county. Data estimates are shown separately from the adjacent counties for Carson City, Nevada.
  7. New York: New York City boroughs
    The five boroughs of New York City have been treated as counties and maintained as separate entities on this file.
    Borough County FIPS Code
    Bronx Bronx 36005
    Brooklyn Kings 36047
    Manhattan New York 36061
    Queens Queens 36081
    Staten Island Richmond 36085
  8. Virginia independent cities:
    1. Alleghany, Virginia
      Alleghany, Virginia (FIPS code 51005) and Clifton Forge city, Virginia (FIPS code 51560) are reported separately.
    2. Clifton Forge city, Virginia
      Clifton Forge city, Virginia (FIPS code 51560) data are reported separately from merged with Alleghany county (FIPS code 51005).
    3. Nansemond city, Virginia
      Nansemond city, Virginia (FIPS code 51123) has been part of the independent city of Suffolk, VA (FIPS code 51800) since 1979. For all years, data for Nansemond city are aggregated and reported with data Suffolk city.
    4. Table of Virginia independent cities and counties
      The Virginia independent cities are treated as counties and appear on the data with the following FIPS codes: 
         Independent City	       County

      Name	    FIPS code	Name	    FIPS code   

      Alexandria	51510	Arlington	51013
Bedford		51515	Bedford		51019
Bristol		51520	Washington	51191
Buena Vista	51530	Rockbridge	51163
Charlottesville	51540	Albemarle 	51003
Chesapeake	51550	
Clifton Forge	51560	Alleghany 	51005 
Colonial Heights51570	Chesterfield 	51041
Covington	51580	Alleghany 	51005
Danville	51590	Pittsylvania 	51143
Emporia		51595	Greensville	51081
Fairfax		51600	Fairfax	 	51059
Falls Church	51610	Fairfax 	51059
Franklin	51620	Southampton	51175
Fredericksburg	51630	Spotsylvania	51177
Galax		51640	Grayson 	51077          
Hampton		51650
Harrisonburg	51660	Rockingham	51165
Hopewell	51670	Prince George	51149
Lexington	51678	Rockbridge	51163
Lynchburg	51680	Campbell 	51031
Manassas	51683	Prince William	51153
Manassas Park	51685	Prince William	51153
Martinsville	51690	Henry	 	51089
Newport News	51700
Norfolk		51710
Norton		51720	Wise	 	51195
Petersburg	51730	Dinwiddie	51053
Poquoson	51735	York	 	51199
Portsmouth	51740	Norfolk city	51710
Radford		51750	Montgomery	51121
Richmond	51760	Henrico	 	51087
Roanoke		51770	Roanoke	 	51161
Salem		51775	Roanoke	 	51161
Staunton	51790	Augusta	 	51015
Suffolk		51800
Virginia Beach	51810
Waynesboro	51820	Augusta	 	51015
Williamsburg	51830	James City	51095
Winchester	51840	Frederick	51069



This page last reviewed: Monday, September 24, 2012
This information is provided as technical reference material. Please contact us at cwus@cdc.gov to request a simple text version of this document.
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