Frost dates / By state
Frost dates in Illinois
NOAA 1991–2020 normals for a 32 °F freeze. Your own yard can run a little either side.
Short answer
Across 22 NOAA weather stations in Illinois, the average last spring frost runs from April 2 at Cairo 3N to April 30 at Chicago Waukegan Rgnl Airport. The first fall frost comes as early as October 10 at Shabbona 5 NNE and as late as October 31 at Chicago Midway Airport. Planting zones near these stations run from 5b to 7a.
Illinois cities
- Frost dates in Chicago: last frost April 11, first frost October 31
- Frost dates in Aurora: last frost April 28, first frost October 13
- Frost dates in Naperville: last frost April 28, first frost October 16
- Frost dates in Joliet: last frost April 19, first frost October 25
- Frost dates in Rockford: last frost April 24, first frost October 17
Find yours by ZIP code
The table below is by weather station. For the station nearest you, and your planting zone, type your ZIP code.
Illinois frost dates by weather station
| Station | Last spring frost | First fall frost | Frost-free | Zone nearby |
|---|---|---|---|---|
| Belleville Siu Rsch 450 ft | April 12 1 in 10 after April 28 | October 20 1 in 10 by October 3 | 191 days | 6b |
| Cahokia St Louis Airport 413 ft | April 8 1 in 10 after April 23 | October 26 1 in 10 by October 12 | 201 days | 7a |
| Cairo 3N 313 ft | April 2 1 in 10 after April 17 | October 31 1 in 10 by October 18 | 212 days | 7a |
| Carbondale Southern Il Airport 406 ft | April 9 1 in 10 after April 25 | October 22 1 in 10 by October 8 | 196 days | 7a |
| Champaign 9 SW 700 ft | April 23 1 in 10 after May 9 | October 13 1 in 10 by September 28 | 173 days | 6a |
| Champaign Willard Airport 754 ft | April 19 1 in 10 after May 5 | October 17 1 in 10 by October 3 | 181 days | 6a |
| Chicago Aurora Muni Airport 710 ft | April 28 1 in 10 after May 11 | October 13 1 in 10 by September 27 | 168 days | 5b |
| Chicago Midway Airport 612 ft | April 11 1 in 10 after April 27 | October 31 1 in 10 by October 20 | 203 days | 6a |
| Chicago Ohare Intl Airport 658 ft | April 16 1 in 10 after May 1 | October 28 1 in 10 by October 15 | 195 days | 6a |
| Chicago Palwaukee Airport 636 ft | April 19 1 in 10 after May 3 | October 26 1 in 10 by October 13 | 190 days | 6a |
| Chicago Waukegan Rgnl Airport 727 ft | April 30 1 in 10 after May 16 | October 21 1 in 10 by October 5 | 174 days | 6a |
| Decatur Airport 675 ft | April 16 1 in 10 after April 30 | October 22 1 in 10 by October 7 | 189 days | 6a |
| Lawrenceville Intl Airport 429 ft | April 8 1 in 10 after April 22 | October 26 1 in 10 by October 13 | 201 days | 6b |
| Mattoon Coles Co Airport 721 ft | April 15 1 in 10 after April 30 | October 24 1 in 10 by October 9 | 192 days | 6a |
| Moline Quad City Intl Airport 592 ft | April 24 1 in 10 after May 9 | October 18 1 in 10 by October 4 | 177 days | 5b |
| Peoria Gtr Peoria Airport 650 ft | April 16 1 in 10 after May 4 | October 23 1 in 10 by October 9 | 190 days | 6a |
| Quincy Rgnl Airport 769 ft | April 14 1 in 10 after May 1 | October 23 1 in 10 by October 10 | 192 days | 6a |
| Rantoul 740 ft | April 21 1 in 10 after May 6 | October 18 1 in 10 by October 5 | 180 days | 6a |
| Rockford Gtr Rockford Airport 730 ft | April 24 1 in 10 after May 8 | October 17 1 in 10 by October 2 | 176 days | 5b |
| Shabbona 5 NNE 861 ft | April 28 1 in 10 after May 13 | October 10 1 in 10 by September 26 | 165 days | 5b |
| Springfield Capital Airport 594 ft | April 14 1 in 10 after April 29 | October 20 1 in 10 by October 5 | 189 days | 6a |
| West Chicago Dupage Airport 754 ft | April 25 1 in 10 after May 12 | October 19 1 in 10 by October 5 | 177 days | 5b |
The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. Stations are NOAA's main weather stations, mostly airports. “Zone nearby” is the USDA 2023 zone of the nearest ZIP code within 10 miles. NOAA counts the frost season from August to July, so in the warmest places the “first fall” freeze lands after New Year.
How these dates work
Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.
The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.
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Where the numbers come from
- USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture
- PRISM Climate Group, Oregon State University (zone data)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal
- NOAA, Normals calculation methodology (frost-freeze probability dates)
- US Census Bureau, 2025 ZCTA gazetteer (ZIP code centers)