Rainfall above normal over much of Illinois during warm September 

[OCT. 8, 2005]  CHAMPAIGN -- Last month was the seventh-warmest September since 1895 and the third-warmest September on record in northeastern Illinois. It was also the fourth consecutive month of temperatures above normal and the seventh-warmest June-September on record.

"September temperatures averaged 70.6 degrees Fahrenheit statewide, 4.4 degrees above normal," said Jim Angel, state climatologist with the Illinois State Water Survey, a division of the Illinois Department of Natural Resources. "Temperatures ranged from 97 degrees Fahrenheit at Belleville on Sept. 22 to 32 degrees Fahrenheit at Mount Carroll on Sept. 29."

September rainfall averaged 0.73 inches above normal, at 3.91 inches, but rainfall since March averaged 18.90 inches, which is 7.12 inches below normal, making this Illinois' sixth-driest March-September since 1895. While most of the state enjoyed the extra rainfall in September, rainfall north of Interstate 80 was only 2.79 inches, which is 0.54 inches below normal. Nashville had the highest one-day precipitation total with 3.58 inches on Sept. 20. Lebanon had the highest monthly total with 10.11 inches.

Across the state, rainfall has remained below normal since March 1. For example:

• Chicago O'Hare Airport received 12.8 inches, 11.9 inches below normal
• Rockford, 16.1 inches, 10.5 inches below normal
• Moline, 10.9 inches, 16.3 inches below normal
• Peoria, 13.2 inches, 11.5 inches below normal
• Quincy, 15.4 inches, 10.6 inches below normal
• Springfield, 16.0 inches, 8.1 inches below normal
• Champaign, 21.3 inches, 6.8 inches below normal
• Carbondale, 21.7 inches, 5.7 inches below normal.

"While good rains in August and September have alleviated drought conditions in portions of central and southern Illinois, the most severely affected area in northern Illinois remains stubbornly dry," Angel says. "Check the ISWS' special drought website for regular updates (http://www.sws.uiuc.edu/hilites/drought/)."

Now that October has arrived, the first fall frost becomes a concern for gardeners. Based on 1971-2000 averages, the first fall frost usually occurs between Oct. 7, in northern Illinois, and Oct. 21, in southern Illinois, with an average date of Oct. 14 in central Illinois. A map for reference is available at http://www.sws.uiuc.edu/atmos/
statecli/Frost/avg_first_fall_frost_map.gif. An interesting feature of the map is the delay in the first frost date by about a week in the Chicago area, probably due to a combination of the warmer urban setting and the moderating influence of Lake Michigan.

Angel points out that the actual frost date varies quite a bit each year. "For planning purposes, you can expect the first frost within two weeks of those dates," he says.

[Illinois Department of Natural Resources news release]