The summaries of daily land surface observations in this data set are primarily from stations in the National Weather Service (NWS) cooperative station network, but also include NWS principal (first order) climatological stations, and stations supported by the Federal Aviation Administration (FAA), National Park Service (NPS), Bureau of Land Management (BLM), U.S. Forest Service (USFC), U.S. Geological Survey (USGS), and Tennessee Valley Authority (TVA), along with a handful of stations at Air Force and Navy bases. The sites are located in the contiguous U.S., Alaska, Puerto Rico, Virgin Islands, Hawaii and other Pacific Islands.

The major parameters are daily weather, precipitation, snowfall, snow depth, maximum temperature, minimum temperature, and observation temperature. The earliest data is for 1890, but most stations begin in 1948. There are currently about 8500 reporting stations. Periods of record vary widely among the stations.