Frost dates for Decatur Airport, IL
At Decatur Airport, the median last spring frost (32°F) is Apr 16 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 16Last 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 26 | May 12 |
| 32°F | Apr 3 | Apr 16 | Apr 30 |
| 28°F | Mar 20 | Apr 5 | Apr 21 |
| 24°F | Mar 8 | Mar 27 | Apr 10 |
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 26 | Oct 11 | Oct 23 |
| 32°F | Oct 7 | Oct 22 | Nov 3 |
| 28°F | Oct 21 | Nov 2 | Nov 17 |
| 24°F | Nov 1 | Nov 14 | Dec 1 |
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 | 145 days | 164 days | 184 days |
| 32°F | 167 days | 187 days | 206 days |
| 28°F | 188 days | 210 days | 231 days |
| 24°F | 212 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 |
|---|---|---|---|
| 62549 | 6a | -10 to -5°F | 7 km |
| 62501 | 6a | -10 to -5°F | 11 km |
| 62554 | 6a | -10 to -5°F | 12 km |
| 61936 | 6a | -10 to -5°F | 12 km |
| 61925 | 6a | -10 to -5°F | 13 km |
| 61818 | 6a | -10 to -5°F | 14 km |
| 61855 | 6a | -10 to -5°F | 20 km |
| 61929 | 6a | -10 to -5°F | 21 km |
| 61830 | 6a | -10 to -5°F | 23 km |
| 61882 | 6a | -10 to -5°F | 32 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 USW00003887, at 39.8344, -88.8656, elevation 206 m (675 ft).
- Data quality: Representative (10+ years), 20 years of freeze data.
- Average days per year at or below 32°F: 113.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Decatur Water Plant (7 km)
- Sullivan 3s (38 km)
- Shelbyville Dam (48 km)
- Champaign 9 SW (49 km)
- Windsor (49 km)
- Tuscola (49 km)
- Lincoln (54 km)
- Champaign Willard Airport (55 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.