Climatic Data for Frost Protected Shallow Foundations

Publications and Data

The 100-year return period of the Air Freezing Index (AFI) is available for 3,110 cities in the continental United States, Alaska, Hawaii, and Puerto Rico. These data can be interpolated from an AFI analyzed map or obtained from data tables ( PDF Format 457K or Excel Spreadsheet Format 676K). The data table publication contains a listing of cities with the specific 100-year return period value located in the far right column. Other columns in the table contain lesser return periods and are listed for comparison purposes or other applications. Only the 100-year return period in this publication should be used for FPSF.

Another publication provides the 29 winter season values that were used to compute the 100-year return period of the AFI. Data tables ( PDF Format 490K or Excel Spreadsheet Format1622K) contain the AFI value for each of the 29 winter seasons from the 1951-80 period for 3,110 cities. These data are used for applications other than FPSF.

Finding a station: To find a station in the publications use the "Find" capability (binocular icon in PDF files; in Excel files, Click Edit and then Find) and enter a city or place name.

All cities do not have Air Freezing Index values located in these files. If your city is not available, you can locate a nearby city by using a station locator system called Web Cliserv.

    1) Once in Web Cliserv first select the city you want but could not find like Cleveland.
    2) Then choose one of the Cleveland stations, possibly Burke Lakefront.
    3) Then under the station name Cleveland Burke Lakefront you will see other options such as:
      a) List stations in Cuyahoga County
      b) Surrounding Stations (+/-30 minutes)
    4) Choose a and/or b to find nearby stations
    5) See if one of these nearby stations has AFI values

Cautionary Note when using Air Freezing Index values: Topographic variability, proximity to bodies of water, and urban heat effects should be considered when using these data. For those locations or if the planned construction site is not located nearby a station that has AFI data, using a combination of the AFI map and the most representative city(s) AFI value(s) is advisable.

PDF Format Excel Spreadsheet Format Air Freezing Index - Return Periods & Associated Probabilities

PDF Format Excel Spreadsheet Format Air Freezing Index - Seasonal Data

This page was developed as a parternership among the National Climatic Data Center, National Association of Home Builders Research Center, and American Society of Civil Engineers.