Frost dates in Chicago, Illinois
NOAA 1991–2020 normals for a 32 °F freeze. Low spots and the edge of town run colder than downtown.
Short answer
The average last spring frost in Chicago is April 11, and the average first fall frost is October 31, from NOAA's Chicago Midway Airport station, 5 miles from the middle of Chicago. 1 year in 10 the last frost comes after April 27, and the first one by October 20. That leaves about 203 frost-free days. Chicago is in USDA planting zone 6a.
Weather stations around Chicago
The first row is the date most people in Chicago go by. The others show how far the dates move across the area.
| Station | Last spring frost | First fall frost | Frost-free |
|---|---|---|---|
| Chicago Midway Airport 5 mi away, 612 ft | April 11 1 in 10 after April 27 | October 31 1 in 10 by October 20 | 203 days |
| Chicago Northerly Is 4 mi away, 583 ft | April 10 1 in 10 after April 25 | November 5 1 in 10 by October 24 | 209 days |
| Chicago Midway Airport 3SW 8 mi away, 620 ft | April 10 1 in 10 after April 26 | November 1 1 in 10 by October 21 | 205 days |
| Little Red School Hse 13 mi away, 715 ft | April 19 1 in 10 after May 5 | October 22 1 in 10 by October 8 | 186 days |
| Chicago Ohare Intl Airport 17 mi away, 658 ft | April 16 1 in 10 after May 1 | October 28 1 in 10 by October 15 | 195 days |
Distances are from the middle of Chicago as the Census Bureau maps it. 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. The planting zone is the USDA 2023 zone for ZIP code 60608, at the middle of the city.
Your exact ZIP code
Chicago covers a lot of ground. For the station nearest your own street, and its planting zone, type your ZIP code.
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.
More frost dates
All of Illinois, station by station.
Other Illinois cities: Aurora · Naperville · Joliet · Rockford
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)
- US Census Bureau, 2025 city population estimates and place gazetteer