The "a" network is the basic climatic network of the NWS.   These data are used to describe the climate of the United States.   At a minimum, "a" network stations must observe 24-hour precipitation totals. nbsp; Many "a" network stations also report maximum and minimum temperatures.

Cooperative observing stations are placed in the "b" network if their observations are used primarily to support NWS hydrologic programs, such as flood forecasting, hydrologic planning, and water supply.   These stations nearly always report 24-hour precipitation and many include river stage or lake level.   A few report maximum and minimum temperatures, water equivalent of snow on the ground, evaporation, and soil temperature.

Cooperative stations that support both the climatological and hydrological programs of the NWS are referred to as being in the "ab" network.   These stations generally have the responsibilities of "a" and "b" network stations combined.

Cooperative stations are placed in the "c" network if they support meteorological programs of the NWS, such as the issuance of warnings, forecasts, and public service.   These stations maintain the same type of observations and equipment as the other networks.

Climatological records get more valuable with time.   The climatological data generated through the efforts of the volunteer Cooperative Weather Observers provides not only the cornerstone of our nation's weather history, but also serves as the primary data for research into global climate change.

On a local level, the observations received by volunteer observers are fundamental in helping the NWS to protect life and property.   Forecasts are often based on observer data.  Sometimes warnings for severe weather have been issued based on information received from a volunteer.   After each month, the local weather office collects all the data provided by local observers and sends it to the National Climatic Data Center (NCDC) in Asheville, NC.   At NCDC, the data is entered into a huge national database that is accessible by the public.

Requests for this data come from a wide array of parties including attorneys, insurance companies, meteorological consultants, businesses including construction, utilities, universities and other educational institutions, transportation companies, agriculture, and the media.

Requests for this data may be referred to:

National Climatic Data Center
Federal Building
151 Patton Ave.
Asheville, NC 28801-5001
828-271-4800 (fax 828-271-4876)