Frost dates for Sullivan 3s, IL
At Sullivan 3s, the median last spring frost (32°F) is Apr 15 and the median first fall frost is Oct 22, for a typical growing season of 187 days. For a 90% chance that the last frost has passed, wait until Apr 30. Nearby ZIP codes are in USDA hardiness zone 6a.
- Apr 15Last spring frost (median)50% chance of 32°F after this date
- Apr 30Safer planting date10% chance of 32°F after this date
- Oct 22First fall frost (median)50% chance of 32°F by this date
- 187 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Apr 13 | Apr 25 | May 13 |
| 32°F | Apr 2 | Apr 15 | Apr 30 |
| 28°F | Mar 20 | Apr 4 | Apr 18 |
| 24°F | Mar 8 | Mar 26 | Apr 8 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Sep 25 | Oct 11 | Oct 24 |
| 32°F | Oct 6 | Oct 22 | Nov 2 |
| 28°F | Oct 20 | Nov 1 | Nov 16 |
| 24°F | Nov 1 | Nov 11 | Nov 29 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 143 days | 164 days | 184 days |
| 32°F | 165 days | 187 days | 207 days |
| 28°F | 189 days | 210 days | 230 days |
| 24°F | 211 days | 232 days | 256 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 61951 | 6a | -10 to -5°F | 4 km |
| 61914 | 6a | -10 to -5°F | 15 km |
| 61937 | 6a | -10 to -5°F | 20 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00118389, at 39.5608, -88.6089, elevation 195 m (640 ft).
- Data quality: Representative (10+ years), 20 years of freeze data.
- Average days per year at or below 32°F: 122.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Windsor (13 km)
- Shelbyville Dam (22 km)
- Mattoon (24 km)
- Neoga 4nw (25 km)
- Mattoon Coles Co Airport (30 km)
- Decatur Airport (38 km)
- Tuscola (38 km)
- Charleston (39 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.