Frost dates in Rockford, 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 Rockford is April 24, and the average first fall frost is October 17, from NOAA's Rockford Gtr Rockford Airport station, 5 miles from the middle of Rockford. 1 year in 10 the last frost comes after May 8, and the first one by October 2. That leaves about 176 frost-free days. Rockford is in USDA planting zone 5b.
Weather stations around Rockford
The first row is the date most people in Rockford go by. The others show how far the dates move across the area.
| Station | Last spring frost | First fall frost | Frost-free |
|---|---|---|---|
| Rockford Gtr Rockford Airport 5 mi away, 730 ft | April 24 1 in 10 after May 8 | October 17 1 in 10 by October 2 | 176 days |
| Beloit 17 mi away, 788 ft | May 1 1 in 10 after May 16 | October 12 1 in 10 by September 28 | 164 days |
| Clinton Wwtp 22 mi away, 924 ft | April 30 1 in 10 after May 17 | October 10 1 in 10 by September 26 | 163 days |
| Marengo 23 mi away, 815 ft | April 28 1 in 10 after May 14 | October 12 1 in 10 by September 28 | 167 days |
| Rochelle 24 mi away, 775 ft | April 26 1 in 10 after May 12 | October 13 1 in 10 by September 29 | 170 days |
Distances are from the middle of Rockford 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 61104, at the middle of the city.
Your exact ZIP code
Rockford 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 · Joliet
Nearby: Madison, WI
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