Backyard weather observers contribute to science

by Lisa Sheppard, Prairie Research Institute

Whether you enjoy watching the weather or hope for more accurate local forecasts, reading a rain gauge in your own backyard as a volunteer to the Community Collaborative Rain, Hail & Snow (CoCoRaHS) network can make a big contribution to spot-on forecasts and studies of precipitation and climate, according to Trent Ford, Illinois State Climatologist at the Illinois State Water Survey (ISWS).

CoCoRaHS is a nationwide non-profit network with about 860 volunteers of all ages in Illinois, but more volunteers are needed to cover various parts of the state. Volunteers check rain gauges at the same time each day, particularly in the early morning, measure any precipitation, and report the results on an app or computer. In this way, they learn more about the weather and how it can affect our lives.

Rainfall observers help to fill the gaps where National Weather Service (NWS) stations are absent. When NWS stations are far apart and few across the state, their reports don’t account for local variability in rainfall. In Champaign County, for instance, Ford noted that last year in two locations just 8 miles apart, one area received 10 more inches of rain than the other.

“Where there are few CoCoRaHS observers, we are asking a lot of the National Weather Service stations to represent large areas that could have significant differences in rainfall,” Ford said. “When thinking in agricultural terms, 10 inches of rain could be the difference between a good crop or one that yields less than expected.”

The daily precipitation measurements that volunteers provide are important for post-event analysis to understand storms and their impacts in the state. Daily and weekly precipitation data are also used to improve predictions for next week’s forecast, Ford said.

“One thing we all share is our concern over the accuracy of weather forecasts.” Ford said. “The CoCoRaHS network makes a huge difference in helping us to understand that day-to-day weather variability.”

Observers are needed in all parts of the state, in rural and urban areas, as rain can appear in one area, but not in another. Weather forecasts are important in both agricultural areas and in cities. The observations contribute to the understanding of where there may be effects from urban or flash flooding.

In Chicago and in smaller cities, most of the CoCoRaHS observers are in the periphery of cities, leaving entire neighborhoods with no collected rain data.

 As a part of daily monitoring, volunteers indicate days when no precipitation occurs, which can be just as important as determining how much rain fell in a day or two. As the State Climatologist, Ford examines indicators for drought every week so he can make state recommendations to the U.S. Drought Monitor, which informs federal and state decisions on drought recovery assistance. 

“It’s really important for me to have data from observers to know where it didn’t rain,” Ford said. “Without the observations, we might assume that the whole county got rainfall. Accurate data are necessary, particularly when parts of the state are going into and out of drought.” 

Researchers also use the observation data in computer models and for studies of weather, climate, and water-related topics, such as streamflow and water supply planning. The data collected from volunteers have proven to be accurate enough to inform research. 

For information about the CoCoRaHS network and to join the effort, visit the CoCoRaHS website at and join at For questions, contact the Illinois State Coordinator Steve Hilberg, hberg@illinois.edu217-377-6034.

Media contacts: Trent Ford,, 217-244-1330; Steve Hilberg,, 217-377-6034

This story originally appeared on the Prairie Research Institute News Blog. Read the original.

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