Talking (and doing) something about the weather

  • Volunteers throughout the county - and the country - check official rain gauges daily and report their readings to CoCoRaHS. Precipitation amounts can vary even within a few miles, and the pinpoint data contributes to research and helps experts predict flooding.

    Volunteers throughout the county - and the country - check official rain gauges daily and report their readings to CoCoRaHS. Precipitation amounts can vary even within a few miles, and the pinpoint data contributes to research and helps experts predict flooding. Laura Stoecker | Staff Photographer, 2008

Published: 1/20/2010 12:02 AM

Every drop counts.

Everyone talks about the weather, but on any given day between 7,500 and 9,000 volunteers across the country take it a step farther. These trained volunteers check their backyard rain gauges and record precipitation. Representing all ages and diverse backgrounds, together the group makes a significant difference in reporting local weather conditions.

The Community Collaborative Rain, Hail and Snow Network with the acronym CoCoRaHS, pronounced "coco-RAHZ," is a nonprofit citizen-based source of reliable data. Program volunteers use a standardized 4-inch plastic rain gauge and interactive Web site to record their daily readings. The information is used to forecast weather and for other atmospheric and hydrologic research.

Minnesota came on board last month, meaning all 50 states are now participating. Arizona and Delaware signed on last fall.

Illinois was the 13th state to join the grass-roots effort. Today, there are 1,137 volunteers statewide, including 86 in DuPage County. In Lisle, eight residents participate and 12 take part in Naperville.

CoCoRaHS continues to seek volunteers, said William Morris, a hydrologist and regional coordinator of CoCoRaHS at the Chicago Area National Weather Service Office in Romeoville.

"The more observers we have throughout the region, the more accurate our assessment of isolated thunderstorms and the amount of rain that actually fell," Morris said. "We gladly will welcome into the program as many as want to join. There are also times when an observer may be on vacation or otherwise unable to report."

It's easy to sign up. The only expense is $25 for the standardized rain gauge that has proved to be very accurate. A free training session will take place in the spring. Details will be available at and click on Illinois.

Each day when it rains or snows, the volunteer takes a few minutes to measure and report on the precipitation from their location. The data appears on the CoCoRaHS Web site. Among the interesting reports was a trace of rain reported at the Lisle locations whereas both Naperville and Downers Grove CoCoRaHS reported heavy rain falls.

In his Jan. 7 newsletter, Illinois CoCoRaHS coordinator Steve Hilberg cited information from Illinois State Climatologist Jim Angel that preliminary statewide data shows 2009 was the fourth wettest year on record with 50.3 inches of precipitation. The wettest year was 1993 (51.2 inches), followed by 2008 (50.5 inches) and 1990 (50.4 inches).

"Once we had reports of six inches of rain over several hours in Rockford, and with our CoCoRaHS we were able to use that information to issue a flash flood warning for that area," Morris said. "We have the radar we can look at, but it is nice having what we call 'ground truth,' individuals actually measuring the rainfall and sending that information to us."

Interesting? Yes.

But more importantly, volunteers are filling in a part of the weather puzzle that never existed before. The data is used by the National Weather Service, meteorologists, hydrologist, farmers, outdoor enthusiasts, emergency workers, mosquito control workers, insurance adjusters, teachers, gardeners and even neighbors simply comparing how much rain fell in their backyards.

Accumulative data helps with climate monitoring, weather prediction and drought assessments. Morris uses the information to issue river forecasts and ice-jamb flooding reports.

"As a hydrologist, the actual reports from observers help to supplement our radar and have proven to be extremely helpful in river forecasting and flooding," Morris said. "When we forecast for a given river, we look at the amount of rainfall within that given river basin. The more reports we get, the more accurate our assessment."

The wealth of information on the CoCoRaHS Web site,, wasn't available a decade ago.

CoCoRaHS began in 1998 in Colorado following a devastating flash flood that took both lives and property in Fort Collins. An extreme local variation dumped 14-inches of rain on portions of the city and its intensity was not captured with existing methods. It drew attention to how different precipitation can be even within one community and between official weather stations. The tragedy also convinced local meteorologists that pinpointed weather observations across a wider area would better serve the community.

Nolan Doesken, who maintains a historic weather station on the Colorado State University campus, was aware of the value of basic observations. He set the stage to start CoCoRaHS.

At first, the project used the help of local high school students and a few dozen volunteers. With a National Science Foundation Informal Science Education grant and funding from the National Oceanic and Atmospheric Administration Office of Education the last three years, the network of volunteers expanded across the country as more people and organizations got involved.

"What always jumps out at us is just how much precipitation varies from place to place, day to day, year to year," Doesken said. "Precipitation is much more variable than most other climate elements, so there is clearly the need for more observation points to better understand the nature of precipitation."

With 10 years of data, Fort Collins researchers learned that one part of the city consistently gets about 25 percent more rain and snow than the opposite side of town. Doesken calls such data the "tip of the iceberg" that longer data records will reveal. It should fill in the gaps to understanding thunderstorms, blizzards and flash flooding.

Anyone with an interest in the weather or the environment is encouraged to participate. For details, go to It takes only five-minutes a day and is a fun way to stay on the cutting edge in any discussion on weather.

• Joan Broz writes about Lisle. E-mail her at