Despite all of the state-of-the-art technology associated with the modernization of the National Weather Service, there is one program that has remained virtually unchanged since its inception over a century ago. This is the "Cooperative Weather Observer Program" where 11,700 volunteer weather observers across the country record daily temperature and precipitation data. Some also record/report additional information such as soil temperature, evaporation and wind movement, agricultural data, water equivalent of snow on the ground, river stages, lake levels, atmospheric phenomena, and road hazards. Many Cooperative Stations in the United States have been collecting weather data from the same location for over 100 years. The Cooperative Network has been recognized as the most definitive source of information on U.S. climate trends for temperature and precipitation. Cooperative Stations form the core of the U.S. Historical Climate Network (USHCN) and the U.S. Reference Climate Network.

Equipment to gather these data is provided and maintained by the National Weather Service. Data forms are sent monthly to the National Climatic Data Center (NCDC) in Asheville, North Carolina, where information is digitized, quality controlled, and  archived. Volunteer weather observers regularly and conscientiously contribute their time so that their observations can provide vital weather and climate information. This data is invaluable in learning more about the floods, droughts, and heat and cold waves which inevitably affect everyone. It is also used in agricultural planning and assessment, engineering, environmental-impact assessment, utilities planning, and litigation and plays a critical role in efforts to recognize and evaluate the extent of human impacts on climate from local to global scales.