Networks
(A)  The "a" network is the basic climatic network of the NWS. Data are used to describe the climate of the U.S. The network is based on a grid system (20 statute miles by 20 statute miles) with one station per grid box. At a minimum, "a" network stations must observer 24-hour precipitation totals. Many also report maximum and minimum temperatures.

(B)  Cooperative 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. Stations nearly always report 24-hour precipitation, and many include river stage or lake level. A few report maximum and minimum temperatures and the water equivalent of snow on the ground. A few stations record evaporation, and soil temperature.

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

(C)  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 that the other networks do.