Frost dates for Willimantic Windham Airport, CT
At Willimantic Windham Airport, the median last spring frost (32°F) is Apr 28 and the median first fall frost is Oct 13, for a typical growing season of 167 days. For a 90% chance that the last frost has passed, wait until May 11. Nearby ZIP codes are in USDA hardiness zone 6b.
- Apr 28Last spring frost (median)50% chance of 32°F after this date
- May 11Safer planting date10% chance of 32°F after this date
- Oct 13First fall frost (median)50% chance of 32°F by this date
- 167 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 27 | May 9 | May 22 |
| 32°F | Apr 17 | Apr 28 | May 11 |
| 28°F | Apr 2 | Apr 14 | Apr 29 |
| 24°F | Mar 17 | Apr 2 | Apr 15 |
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 23 | Oct 3 | Oct 16 |
| 32°F | Oct 2 | Oct 13 | Oct 29 |
| 28°F | Oct 10 | Oct 25 | Nov 7 |
| 24°F | Oct 21 | Nov 5 | Nov 22 |
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 | 129 days | 146 days | 164 days |
| 32°F | 149 days | 167 days | 189 days |
| 28°F | 170 days | 193 days | 213 days |
| 24°F | 196 days | 217 days | 237 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 |
|---|---|---|---|
| 06256 | 6b | -5 to 0°F | 2 km |
| 06226 | 6b | -5 to 0°F | 4 km |
| 06280 | 6b | -5 to 0°F | 7 km |
| 06266 | 6b | -5 to 0°F | 8 km |
| 06264 | 6b | -5 to 0°F | 8 km |
| 06237 | 6b | -5 to 0°F | 11 km |
| 06249 | 6b | -5 to 0°F | 13 km |
| 06231 | 6b | -5 to 0°F | 19 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 USW00054767, at 41.7419, -72.1836, elevation 75 m (247 ft).
- Data quality: Standard (24+ years of data), 24 years of freeze data.
- Average days per year at or below 32°F: 135.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Storrs (7 km)
- Hampton (11 km)
- Norwich Public Utility Plant (26 km)
- Staffordville (29 km)
- W Thompson Lake (32 km)
- Hartford Brainard Field (39 km)
- Groton (45 km)
- Hartford Bradley Intl Airport (47 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.