It’s Almost Time for First Fall Frost in Illinois, Illinois State Water Survey

Press Release

For Immediate Release September 25, 2002
It’s Almost Time for First Fall Frost in Illinois
Jim Angel - (217) 333-0729, Fax: (217) 244-0220,
Eva Kingston - (217) 244-7270, Fax: (217) 333-6540,
Leaves just starting to show some color, chrysanthemums and asters in bloom, the beginning of the harvest season, and cooler night temperatures all signal fall’s arrival in Illinois.

“The first fall frost usually occurs between October 7 (northern Illinois), October 14 (central Illinois), and October 21 (southern Illinois). The Chicago area can expect frost by October 14, a week later than the rest of northern Illinois, probably a result of the warmer urban setting and the moderating influence of Lake Michigan,” says State Climatologist Jim Angel of the Illinois State Water Survey (, a division of the Illinois Department of Natural Resources.

This graphic shows first frost times in Illinois that range from October 7th to October 21st.
(Click to Enlarge Image)

The average frost date is based on 1971-2000 averages. Although the actual date varies quite a bit from year to year, “ frost usually occurs within two weeks of the dates shown on the map,” says Angel.

“Despite concerns about global warming, the first fall frost date has been occurring a little earlier at most Illinois locations since the early 1970s, suggesting somewhat cooler fall conditions,” says Angel.

Data from 13 long-term cooperative observer sites in more rural locations throughout Illinois indicate that the frost date is 16 days earlier in McLeansboro; 14 days earlier in Anna and Champaign-Urbana; 9 days earlier in Hoopeston and Windsor; 7 days earlier in Sparta; and 5 days earlier in Marengo, Walnut, and Minonk. This pattern appears to be prevalent across Illinois, except for a slight trend toward frost 3 days later in Carlinville (west-central), 1 day later in Rushville (northeast), and no change in Mt. Carroll and Aledo.

“There’s a good chance that Indian Summer, a warm, dry spell after the first fall frost, will occur this year. If so, more mild weather will follow,” concludes Angel.

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