Community Collaborative Rain, Hail and Snow Network

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The CoCoRaHS logo.

The Community Collaborative Rain, Hail and Snow Network, or CoCoRaHS, is a network of volunteer weather observers in the United States and Canada that take daily readings of precipitation and report them to a central data store over the internet.


The network was started in 1997, in Larimer County, Colorado after a flash flood in Spring Creek caused damage to structures in the city of Fort Collins, Colorado and killed five people. It also caused $200,000,000 in damages.[2] The severity of the flood surprised meteorologists, until then-assistant state climatologist Nolan Doesken began collecting rainfall measurements from private citizens in the area. About 300 responded to his emergency request. Said Doesken later, "The results of the data showed that more than 14 in. (36 cm) of rain fell over southwest Fort Collins, the area where the flood waters originated, while less than 2 in. (5 cm) of rain fell only 3-4 mi (5-6 km) east. The enthusiastic interest shown by volunteers and the great value of the data verified the need for such a service, and CoCoRaHS was born."[3] The program was originally confined to Colorado (the first "Co" in "CoCoRaHS" stood for "Colorado" instead of "Community"), but began expanding to other states during the 2000s.

A 4-inch plastic rain gauge, typical of those used by the CoCoRaHS program


CoCoRaHS is used by a wide variety of organizations and individuals. The National Weather Service (NWS), other meteorologists, hydrologists, emergency managers, city utilities (water supply, water conservation, storm water), insurance adjusters, the USDA, engineers, mosquito control, ranchers and farmers, outdoor & recreation interests, teachers, students, and neighbors in the community are examples of people who use CoCoRaHS data.

Other programs[edit]

A similar program, the Significant Weather Observing Program (SWOP), was begun independently in around the year 2000 by the National Weather Service Lincoln, Illinois. CoCoRaHS data supplements the more rigorous data from national cooperative weather observers with increased spatial and temporal resolution. Real-time data is also provided by the Citizen Weather Observer Program (CWOP), whose users operate weather stations that automatically report over the internet, and which supplements the more rigorous data reported by formal surface weather observation stations.


The National Oceanic and Atmospheric Administration (NOAA) and the National Science Foundation (NSF) are major sponsors of CoCoRaHS. Other organizations have contributed either financially, and/or with supplies and equipment. Many other organizations and individuals have also pitched in time and resources to help keep the network up and running.


All fifty states and the District of Columbia now participate in CoCoRaHS. Canada joined the network in 2012.[1]

See also[edit]


  1. ^ [1]

External links[edit]