Data in these tables are primarily from the National Weather Service (NWS) cooperative station network. The vast majority of the observers are volunteers (non-paid, private individuals). However, the cooperative network also includes the NWS principal climatological stations, which are operated by highly trained observers. Data from Automatic Surface Observing System (ASOS) stations are also included in the tables and have "airport" in their station names.
Information appearing on this web page has been gathered from the National Climatic Data Center's (NCDC) GHCN (Global Historical Climatology Network)-Daily dataset. GHCN-Daily is an integrated database of daily climate summaries from land surface stations across the globe and is comprised of daily climate records from numerous sources that have been integrated and subjected to a common suite of quality assurance reviews. (Note: Currently, GHCN-Daily data in most of the tables are confined to January 2011 forward (older data reflect NCDC datasets 3206 and 3200), but eventually GHCN-Daily should comprise the entire period of record). To learn more about GHCN-Daily, go here: http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/.