Frost dates for Fitchburg Muni Airport, MA
At Fitchburg Muni Airport, the median last spring frost (32°F) is Apr 29 and the median first fall frost is Oct 11, for a typical growing season of 164 days. For a 90% chance that the last frost has passed, wait until May 13. Nearby ZIP codes are in USDA hardiness zones 6a to 6b.
- Apr 29Last spring frost (median)50% chance of 32°F after this date
- May 13Safer planting date10% chance of 32°F after this date
- Oct 11First fall frost (median)50% chance of 32°F by this date
- 164 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 29 | May 9 | May 24 |
| 32°F | Apr 19 | Apr 29 | May 13 |
| 28°F | Apr 4 | Apr 16 | Apr 29 |
| 24°F | Mar 23 | Apr 3 | Apr 16 |
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 20 | Oct 1 | Oct 13 |
| 32°F | Oct 1 | Oct 11 | Oct 27 |
| 28°F | Oct 9 | Oct 23 | Nov 5 |
| 24°F | Oct 21 | Nov 4 | Nov 19 |
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 | 126 days | 144 days | 160 days |
| 32°F | 147 days | 164 days | 183 days |
| 28°F | 170 days | 188 days | 206 days |
| 24°F | 195 days | 212 days | 231 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 |
|---|---|---|---|
| 01453 | 6a | -10 to -5°F | 4 km |
| 01462 | 6a | -10 to -5°F | 4 km |
| 01464 | 6a | -10 to -5°F | 10 km |
| 01523 | 6b | -5 to 0°F | 10 km |
| 01564 | 6a | -10 to -5°F | 12 km |
| 01434 | 6a | -10 to -5°F | 12 km |
| 01561 | 6b | -5 to 0°F | 13 km |
| 01432 | 6a | -10 to -5°F | 15 km |
| 01510 | 6a | -10 to -5°F | 16 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 USW00004780, at 42.5519, -71.7558, elevation 106 m (348 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 137.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Fitchburg COOP (8 km)
- Ashburnham (15 km)
- Ashburnham N (19 km)
- Barre Falls Dam (26 km)
- Maynard 2 (29 km)
- Birch Hill Dam (31 km)
- Worcester Regional Airport (33 km)
- Lowell (34 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.