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About CoCoRaHS


The Community Collaborative Rain, Hail & Snow network (CoCoRaHS) is a community-based network of volunteers who report rain and snow observations from their own backyards. Reports are used by many people and organizations, including the National Weather Service. Additional rain and snow information from volunteer observers has been used to improve river forecasts or assessment of drought.




Precipitation can be highly variable over short distances. This was illustrated during a significant flash flood which occurred in Fort Collins, CO, in 1998. Researchers determined that the heaviest rainfall occurred away from official rain gauges, but some private rain gauges captured the heaviest rainfall. CoCoRaHS was formed after this event and has since spread across the country.

Learn more about the history of CoCoRaHS

Who Can Participate

CoCoRaHS is open to anyone with an interest in observing weather in their area. Volunteers report rain and snow information once per day in the morning (even if there was no accumulation) using a standardized 4-inch rain gauge. Time commitment is a few minutes a day. Volunteers purchase the rain gauge. Typical observations are rain accumulation and snow accumulation, but observers can also measure the liquid equivalent in snow cover and report hail size.

Click here for an application to join CoCoRaHS

Contact CoCoRaHS


Contact information for Illinois

Contact information for Indiana

Where are Volunteer Observers Needed?


Observations from additional CoCoRaHS observers would be helpful anywhere, but some parts of northeast Illinois and northwest Indiana have few precipitation observations - official or volunteer. Learn more about area river basins and where additional observations could help the most below.