National Weather Service Cooperative Observers volunteer their time to record and report weather observations on a daily basis. They observe daily maximum and minimum temperatures, rainfall, snowfall, and snow depth. Their measurements summarize 24-hour periods ending at an observation time convenient for the volunteer, most often 7:00 AM or 8:00 AM. The data are used to support National Weather Service weather and hydrological forecasts and warnings, and to build the nation's climate record.
In addition, the National Weather Service and the Federal Aviation Administration operate automated weather stations at many of the nation's airports. Data from these stations are augmented by on-site manual observations for those elements difficult to measure by automation (snowfall, snow depth).
The map at left depicts monitoring locations from both of these networks that were active within the past two years. Clicking on a station marker will provide information about the station's history and permits users to retrieve climate data for the station's full period of record.
More full-featured tools for retrieving these data are available from the Midwestern Regional Climate Center, and National Weather Service NOWData.