Frost dates in Joliet, 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 Joliet is April 19, and the average first fall frost is October 25, from NOAA's Joliet Brandon Rd Dam station, 2 miles from the middle of Joliet. 1 year in 10 the last frost comes after May 7, and the first one by October 12. That leaves about 189 frost-free days. Joliet is in USDA planting zone 5b.
Weather stations around Joliet
The first row is the date most people in Joliet go by. The others show how far the dates move across the area.
| Station | Last spring frost | First fall frost | Frost-free |
|---|---|---|---|
| Joliet Brandon Rd Dam 2 mi away, 543 ft | April 19 1 in 10 after May 7 | October 25 1 in 10 by October 12 | 189 days |
| Romeoville Wfo 7 mi away, 660 ft | April 20 1 in 10 after May 6 | October 22 1 in 10 by October 7 | 185 days |
| Channahon Dresden Isl Dam 11 mi away, 505 ft | April 16 1 in 10 after May 3 | October 26 1 in 10 by October 13 | 193 days |
| Morris 1 NW 18 mi away, 524 ft | April 20 1 in 10 after May 6 | October 23 1 in 10 by October 9 | 186 days |
| Little Red School Hse 19 mi away, 715 ft | April 19 1 in 10 after May 5 | October 22 1 in 10 by October 8 | 186 days |
Distances are from the middle of Joliet 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 60431, at the middle of the city.
Your exact ZIP code
Joliet 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: Chicago · Aurora · Naperville · 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