Coldest July on record for Illinois

[August 04, 2009]  CHAMPAIGN -- Based on preliminary data for Illinois, the statewide average temperature for July was 70.4 degrees, 5.3 degrees below normal. This ranks as the coldest July in the statewide records and a degree colder than the previous record, set in 1924 (71.5 degrees), according to Jim Angel, state climatologist, of the Illinois State Water Survey.

Furthermore, while southern Illinois reported a few days with temperatures in the 90s in July, much of the rest of the state has seen none. The normal range of days in the 90s is typically between five in northern Illinois to 15 in southern Illinois.

One clear impact has been a lowered energy demand for cooling homes and businesses during July. Cooling degree days were down 48 percent from normal during this time. Meanwhile, modified growing degree days, a measure of corn development, were down 17 percent from normal, suggesting less favorable growing conditions.

Statewide precipitation for July was 4.9 inches, 1.1 inches above normal. Precipitation since Jan. 1 stands at 29.0 inches, 5.6 inches above normal.

Historically, a cool July is most often followed by a cool August. The specific odds on August temperatures after a cool July are a 45 percent chance for cooler than normal, 34 percent for near normal and 21 percent for above normal. The National Oceanic and Atmospheric Administration Climate Prediction Center indicates that cooler-than-normal temperatures are likely to prevail across Illinois during August and for the northern two-thirds of the state during the August-October period.

The Illinois State Water Survey at the University of Illinois at Urbana-Champaign, under the Institute of Natural Resource Sustainability, is the primary agency in Illinois concerned with water and atmospheric resources.

[Text from file received from the Illinois State Water Survey]