Frost dates for Decatur Water Plant, IL
At Decatur Water Plant, the median last spring frost (32°F) is Apr 14 and the median first fall frost is Oct 24, for a typical growing season of 192 days. For a 90% chance that the last frost has passed, wait until May 1. Nearby ZIP codes are in USDA hardiness zone 6a.
- Apr 14Last spring frost (median)50% chance of 32°F after this date
- May 1Safer planting date10% chance of 32°F after this date
- Oct 24First fall frost (median)50% chance of 32°F by this date
- 192 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 12 | Apr 26 | May 13 |
| 32°F | Apr 1 | Apr 14 | May 1 |
| 28°F | Mar 18 | Apr 3 | Apr 17 |
| 24°F | Mar 7 | Mar 24 | Apr 7 |
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 30 | Oct 14 | Oct 27 |
| 32°F | Oct 11 | Oct 24 | Nov 5 |
| 28°F | Oct 20 | Nov 3 | Nov 19 |
| 24°F | Oct 30 | Nov 12 | 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 | 147 days | 170 days | 190 days |
| 32°F | 171 days | 192 days | 211 days |
| 28°F | 195 days | 214 days | 237 days |
| 24°F | 213 days | 236 days | 258 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 |
|---|---|---|---|
| 62523 | 6a | -10 to -5°F | 2 km |
| 62521 | 6a | -10 to -5°F | 3 km |
| 62532 | 6a | -10 to -5°F | 6 km |
| 62522 | 6a | -10 to -5°F | 8 km |
| 62526 | 6a | -10 to -5°F | 9 km |
| 62514 | 6a | -10 to -5°F | 11 km |
| 62535 | 6a | -10 to -5°F | 11 km |
| 62537 | 6a | -10 to -5°F | 12 km |
| 62544 | 6a | -10 to -5°F | 14 km |
| 62573 | 6a | -10 to -5°F | 17 km |
| 62551 | 6a | -10 to -5°F | 18 km |
| 62513 | 6a | -10 to -5°F | 21 km |
| 61756 | 6a | -10 to -5°F | 23 km |
| 62543 | 6a | -10 to -5°F | 23 km |
| 62550 | 6a | -10 to -5°F | 24 km |
| 62547 | 6a | -10 to -5°F | 26 km |
| 62539 | 6a | -10 to -5°F | 26 km |
| 62567 | 6a | -10 to -5°F | 29 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 USC00112193, at 39.8289, -88.9506, elevation 195 m (639 ft).
- Data quality: Representative (10+ years), 24 years of freeze data.
- Average days per year at or below 32°F: 110.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Decatur Airport (7 km)
- Sullivan 3s (42 km)
- Lincoln (49 km)
- Shelbyville Dam (49 km)
- Windsor (52 km)
- Pana (52 km)
- Champaign 9 SW (55 km)
- Tuscola (56 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.