Frost dates for 01450Groton, MA
The average last spring frost in Groton is April 29 and the average first fall frost is October 11, giving a typical growing season of about 164 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 29
- Average first fall frost
- Oct 11
- Growing season
- 164 days
Safer after May 13 (1-in-10 risk)
Possible by Oct 1 (1-in-10 risk)
Last frost typically in 180 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 29 · May 9 · May 24 | Sep 20 · Oct 1 · Oct 13 | 144 days | 100% |
| Frost / freeze (32°F) | Apr 19 · Apr 29 · May 13 | Oct 1 · Oct 11 · Oct 27 | 164 days | 100% |
| Hard freeze (28°F) | Apr 4 · Apr 16 · Apr 29 | Oct 9 · Oct 23 · Nov 5 | 188 days | 100% |
Planting calendar for Groton
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 29 – Jun 4 |
| Tomatoes | Transplant outdoors | May 15 – Jun 21 |
| Peppers | Start seeds indoors | Mar 29 – Apr 29 |
| Peppers | Transplant outdoors | May 29 – Jun 29 |
| Eggplant | Start seeds indoors | Apr 15 – May 14 |
| Eggplant | Transplant outdoors | May 29 – Jun 29 |
| Cucumbers | Sow outdoors | May 29 – Jul 1 |
| Summer squash | Sow outdoors | May 15 – Jun 29 |
| Winter squash & pumpkins | Sow outdoors | May 29 – Jun 29 |
| Snap beans | Sow outdoors | May 15 – Jul 24 |
| Sweet corn | Sow outdoors | May 15 – Jun 21 |
| Watermelon & cantaloupe | Sow outdoors | May 29 – Jun 29 |
| Okra | Sow outdoors | May 22 – Jun 14 |
| Peas | Sow outdoors (spring) | Mar 29 – May 14 |
| Potatoes | Plant outdoors (spring) | Mar 29 – May 29 |
| Onions | Start seeds indoors (spring) | Feb 15 – Mar 14 |
| Onions | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (spring) | Mar 11 – Apr 14 |
| Broccoli | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (fall) | Jun 11 – Jun 21 |
| Broccoli | Transplant outdoors (fall) | Jul 11 – Jul 22 |
| Cabbage | Start seeds indoors (spring) | Mar 1 – Mar 29 |
| Cabbage | Transplant outdoors (spring) | Mar 29 – Apr 29 |
| Cabbage | Start seeds indoors (fall) | Jun 1 – Jul 1 |
| Cabbage | Transplant outdoors (fall) | Jul 1 – Aug 1 |
| Leaf lettuce | Sow outdoors (spring) | Mar 29 – Jun 14 |
| Leaf lettuce | Sow outdoors (fall) | Jul 1 – Aug 17 |
| Spinach | Sow outdoors (spring) | Mar 22 – May 5 |
| Spinach | Sow outdoors (fall) | Jul 18 – Aug 22 |
| Radishes | Sow outdoors (spring) | Mar 29 – May 19 |
| Radishes | Sow outdoors (fall) | Jul 1 – Sep 1 |
| Kale | Sow outdoors (spring) | Apr 15 – May 5 |
| Kale | Sow outdoors (fall) | Jun 24 – Aug 1 |
| Carrots | Sow outdoors (spring) | Apr 29 – Jun 14 |
| Carrots | Sow outdoors (fall) | Jun 1 – Jul 17 |
| Garlic | Plant outdoors (fall) | Oct 1 – Nov 1 |
Where these dates come from
ZIP code 01450 is matched to the NOAA station Fitchburg Muni Ap, MA, 17.5 km away, at 348 ft elevation (65 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Fitchburg Muni Ap, MA (used) | 348 ft | Apr 29 | Oct 11 |
| Nashua Cwsu, NH | 180 ft | Apr 29 | Oct 8 |
| Lowell, MA | 110 ft | Apr 30 | Oct 10 |
| Fitchburg Coop, MA | 665 ft | May 1 | Oct 9 |
Frost dates near Groton
- Groton, MA 01470 · last Apr 29, first Oct 11
- West Groton, MA 01472 · last Apr 29, first Oct 11
- Ayer, MA 01432 · last Apr 29, first Oct 11
- Pepperell, MA 01463 · last May 3, first Oct 5
- Shirley, MA 01464 · last Apr 29, first Oct 11
- Dunstable, MA 01827 · last May 3, first Oct 8
- Devens, MA 01434 · last Apr 29, first Oct 11
- Littleton, MA 01460 · last May 2, first Oct 6
Frequently asked questions
- When is the last frost in Groton, MA?
- For ZIP code 01450, the average last spring frost (32°F) is April 29, based on NOAA 1991-2020 climate normals for the Fitchburg Muni Ap, MA weather station. There is a 1-in-10 chance of a frost after May 13.
- When is the first frost in Groton, MA?
- The average first fall frost (32°F) is October 11. There is a 1-in-10 chance of frost by October 1, so tender plants are at risk from that point on.
- How long is the growing season in 01450?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 164 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.