Customized Weather History

Terms and Limitations

The Old Farmer's Almanac and Almanac.com are owned by Yankee Publishing Inc. (YPI).

Source of Weather History Data

Raw data for the Customized Weather History feature of Almanac.com comes from the Global Surface Summary of Day from the National Climatic Data Center (NCDC). The NCDC places the following limitations on the use of their data:

The following [Global Surface Summary of Day] data and products may have conditions placed on their international commercial use. They can be used within the U.S. or for noncommercial international activities without restriction. The non-U.S. data cannot be redistributed for commercial purposes. Redistribution of these data by others must provide this same notification. For details, consult Review of Commercial Activities in Meteorology.

Limitations of Data

Data obtained from using our Customized Weather History application is only as complete and accurate as the information obtained from NCDC. Known limitations:

Weather stations come in and out of service; as a result, complete weather data is rarely available for any one specific weather station. Our application makes allowances for this limitation by always finding the most complete data for the location closest to the location you specify for each date you've specified.
Not every weather station records a complete set of temperature, precipitation, wind, snow depth, and pressure data for each date. Our application makes allowances for this limitation by finding the most complete set of data for each location for each date, but there are still situations in which data presented will not be complete; for each data point in the search results, we present the number of data for which data was present.
You may encounter situations where Occurrences data appears to conflict with the numerical data. For example, you may encounter situations where an "occurrence" of rain is noted, but the "total daily precipitation" is recorded as "0". Or vice versa. This is simply because of the limitations in the NCDC data set noted above: not all data points are present for every date, and sometimes "occurrences" are logged but totals are not, or vice versa.

Limitations of Service

The Customized Weather History application is data-intensive -- our server searches through millions of data records to produce your search results. As a result, searches can take up to one minute to complete (although they are often much faster). In general, the more years you include in a date range, the longer the search will take.

The Almanac.com Web server through which Customized Weather History is accessed may be unavailable to you for periods of time due to system maintenance, network congestion or downtime, or other factors.

There is a schedule window for data updates every morning at 5:00 a.m. Eastern Time during which the Customized Weather History may be unavailable.

Data for download (under the POWER ACCESS version of the search) is made available as tab-delimited ASCII text files, suitable for import into most spreadsheet and database programs. YPI cannot provide technical support for use of the data once downloaded.