Join the Community Collaborative Rain, Hail & Snow Network (CoCoRaHS)
In this collaborative, volunteers measure and help map precipitation
Volunteer to help collect precipitation data
The field of participatory science invites people from all walks of life to assist in research that builds our understanding of nature. For more than 25 years, the Community Collaborative Rain, Hail & Snow Network, or CoCoRaHS, has organized volunteers to record precipitation in their locale. The organization maps the observations and makes the data available to the public as well as scientists, resource managers and others responsible for predicting and responding to climatic conditions and weather events.
CoCoRaHS history
CoCoRaHS began in 1998 in Fort Collins, Colorado, as the Colorado Collaborative Rain and Hail Study. Funded by a grant and organized with the assistance of several high school students, the project recruited local residents to measure and report precipitation each day. This data was then shared online so that the public and officials could track and compare local conditions.
Part of the impetus for the project was a 1997 flash flood from Spring Creek. In this event, 13 inches of rain fell on the west side of Fort Collins, while the east side experienced just light rain. Because no one reported the heavy rain to the National Weather Service (NWS), no flood warning was issued. Eastern residents remained unaware of the rising creek, which flowed in their direction, and five people died.
A growing network
As the project gained momentum it spread into nearby communities, neighboring states and beyond. With assistance from Colorado State University and the National Science Foundation, not only did the network of volunteers grow, but the organization also kept up with technological advances.
By 2005, CoCoRaHS was able to nearly instantly transmit hail and heavy rain reports to the NWS. In 2016, observers gained the option to complete weekly condition reports (rated wet, normal or dry) in addition to daily precipitation measurements. This information has been used to help track drought.
How CoCoRaHS works
Today, CoCoRaHS has volunteer weather observers in all 50 states, Canada, several U.S. territories and the Bahamas. People of all ages are welcome to participate. Volunteers provide their address and longitude/latitude (if available) for mapping purposes, and receive an official station number and station name (referencing their municipality) for their location.
There are just two requirements to join:
- Participate in free training (online or in person)
- Obtain a high-quality, NWS-approved manual rain gauge
Finding the correct rain gauge
Although there are many rain gauges on the market, only three versions meet the standards for use in CoCoRaHS reporting. These three share key details, such as a four-inch diameter and the ability to measure to the nearest hundredth of an inch. The CoCoRaHS website lists all three along with links to retail suppliers.
Training for volunteers
Training covers how and where to install the rain gauge, how to accurately read a measurement for rain or snow and how to describe hail. It also shows volunteers how to submit their daily report form—even if it’s zero—using either the CoCoRaHS website or its app. While daily reports are best, observers can also submit cumulative reports covering a range of days, allowing for vacations and such.
Volunteers are also encouraged to submit “significant weather reports” as warranted. Entered at any time that heavy rain or snow is occurring, these are relayed to a local NWS office to assist with the issuance of watches and warnings.
Tracking the data
Meanwhile, observers’ regular recordings appear on maps for anyone to access at cocorahs.org. Data, which can be sorted by state and station number/name, appears in daily lists as well as summaries of date ranges and years. This material allows volunteers as well as the general public to know just how much precipitation a location has received and to compare that to nearby locales. The difference in amounts at spots separated by just a few miles can be startling.
In addition to gathering and sharing precipitation data, CoCoRaHS also aims to educate the public on weather and grow an interest in meteorology. To that end, the organization offers lesson plans for teachers as well as resources aimed at Master Gardeners and others on its website.
Get involved with CoCoRaHS
- Community Collaborative Rain, Hail & Snow Network
- Open to: Anyone. Current participants live in all 50 states, several U.S. territories, Canada and the Bahamas
- Runtime: Year-round
- Enrollment: Sign up any time
- Cost: Free, but you must purchase a high-quality rain gauge
- Learn more: cocorahs.org
Image credit: Famartin/Own Work, CC BY-SA 3.0
