Frost dates for Fitchburg COOP, MA
At Fitchburg COOP, the median last spring frost (32°F) is May 1 and the median first fall frost is Oct 9, for a typical growing season of 162 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 1Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 9First fall frost (median)50% chance of 32°F by this date
- 162 daysGrowing season (median)between 32°F freezes
USDA hardiness zone 6a (-10 to -5°F) · see all zone 6a frost dates
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 30 | May 12 | May 26 |
| 32°F | Apr 19 | May 1 | May 14 |
| 28°F | Apr 5 | Apr 18 | May 1 |
| 24°F | Mar 25 | Apr 4 | Apr 18 |
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 17 | Oct 1 | Oct 11 |
| 32°F | Sep 29 | Oct 9 | Oct 26 |
| 28°F | Oct 5 | Oct 21 | Nov 7 |
| 24°F | Oct 17 | Nov 4 | 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 | 121 days | 140 days | 158 days |
| 32°F | 144 days | 162 days | 181 days |
| 28°F | 165 days | 186 days | 207 days |
| 24°F | 191 days | 212 days | 236 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 |
|---|---|---|---|
| 01420 | 6a | -10 to -5°F | 4 km |
| 01431 | 6a | -10 to -5°F | 7 km |
| 01474 | 6a | -10 to -5°F | 8 km |
| 01469 | 6a | -10 to -5°F | 10 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 USC00192807, at 42.6167, -71.8017, elevation 203 m (665 ft).
- Data quality: Estimated from nearby stations (2+ years), 2 years of freeze data.
- Average days per year at or below 32°F: 147.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Fitchburg Muni Airport (8 km)
- Ashburnham (9 km)
- Ashburnham N (12 km)
- Birch Hill Dam (26 km)
- Barre Falls Dam (28 km)
- Tully Lake (35 km)
- Lowell (36 km)
- Maynard 2 (36 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.