Co-sponsored by the National Oceanic and Atmospheric Administration and the National Science Foundation, CoCoRaHS is for citizen scientists of all ages and from all walks of life who can spend a few minutes per day collecting information on precipitation in their area. Volunteers register their location on the project website and can train themselves online or in person with a local coordinator. By following a set of simple procedures and using a standardized rain gauge, volunteers measure and report their daily amount of rain (or melted snow) on the project website, making the data readily available in a centralized database at the touch of a fingertip. Options to report hail and/or other kinds of weather are also available, as well as advanced options such as evapotranspiration and drought impact reports.
From its origins in Colorado, word of CoCoRaHS spread, and scientists began requesting support for data collection across the United States. CoCoRaHS responded by offering newly participating states access to its technological platform but requiring each state to establish its own network of volunteer leaders responsible for recruiting, training and retaining local monitors. Motivated local leaders have helped expand CoCoRaHS to more than 20,000 active volunteers in all 50 states as well as Washington, D.C. (including the White House!), Puerto Rico, the U.S. Virgin Islands and most provinces in Canada.
A full case study of CoCoRaHS is located in the Federal Crowdsourcing and Citizen Science Toolkit, http://crowdsourcing-toolkit.sites.usa.gov/cocorahs-precipitation/