A high-density raingage network identified large differences in rainfall amounts from June 26-27 storms across Champaign County, Illinois. Amounts ranged from 2.58 inches just west of the I-57/I-72 interchange (west of Champaign) to less than 0.20 inch (southeast Urbana).

Summer rainfall is highly variable as individual thunderstorms produce significant rainfall over small areas (see map [pdf ~350k]). For example, one station reported 2.49 inches while another station 3 miles to the south reported only 0.16 inch, a 2.33-inch difference. Most rain fell between 10:30 a.m. and noon on June 26. Another storm early on June 27 produced another 0.20 to 0.40 inch across parts of Champaign-Urbana.

While official records for Champaign-Urbana date back to 1888 at the Illinois State Water Survey or ISWS (http://www.sws.uiuc.edu/atmos/statecli/Champ-Urb/CU.htm), volunteers in a wider network provide much more detail on such events. The Boneyard Network has operated in the Champaign-Urbana area for years, mainly with data from ISWS employees. That network is merging with the much larger Community Collaborative Rain, Hail, and Snow network or CoCoRaHS (www.cocorahs.org) that covers Champaign County, the rest of Illinois, and is part of a rapidly expanding national volunteer network. The map has data mainly from CoCoRaHS participants. Data from the two volunteer networks should not be regarded as official quality assured ISWS records.

Amounts from both storms exceeded 2.20 inches in southwestern Champaign and north-central Champaign-Urbana between Springfield Avenue and I-74. At the ISWS, 1.34 inches brought the June total to 4.54 inches, 0.33 inch above normal. Until this week, "abnormally dry" conditions in Champaign County affected crops, lawns, and gardens, and put the area on the U.S. Drought Monitor (http://drought.unl.edu/dm/monitor.html). Recent rains have eased those concerns, however.