CoCoRaHS (Community Collaborative Rain, Hail and Snow Network), is managed by the Colorado Climate Center at Colorado State University. Founded in 1998, CoCoRaHS consists of more than 20,000 citizens reporting daily precipitation totals with backyard rain gauges. There are CoCoRaHS volunteers in every state as well as Canada, Puerto Rico, the U.S. Virgin Islands and the Bahamas.
Every spring, The CoCoRaHS Cup goes to the two states that recruit the most volunteers during the month of March (although you can become a volunteer at any time). Small and large states compete separately – one winner for sheer number of new observers, and the other based on the number of new observers per state population. Delaware and Arizona won last year.
Sign up to be a volunteer here.