Westford, MA planting zone & frost dates

Westford is in USDA hardiness zone 6a. The last spring frost usually comes around April 30 and the first fall frost around October 10, for a growing season of about 164 days.

USDA hardiness zone6aavg. extreme winter low -10°F to -5°F

Average last spring frostApril 3090% chance of no frost after May 10

Average first fall frostOctober 1010% chance of frost by September 30

Growing season164 daysfrost-free days in an average year

Planting calendar for Westford

Dates are counted from the average last spring frost (April 30) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.

Crop	When
Tomatoes	Start seeds indoors: Mar 5 – Mar 19 Transplant outdoors: May 7 – May 14
Peppers	Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21
Eggplant	Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21
Broccoli	Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16
Cabbage	Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16
Onions (sets)	Plant outdoors: Apr 2 – Apr 16
Peas	Sow outdoors: Mar 19 – Apr 2
Spinach	Sow outdoors: Mar 19 – Apr 2
Lettuce	Sow outdoors: Apr 2 – Apr 16
Carrots	Sow outdoors: Apr 2 – Apr 16
Potatoes	Plant outdoors: Apr 2 – Apr 16
Beans	Sow outdoors: May 7 – May 14
Sweet corn	Sow outdoors: May 7 – May 14
Cucumbers	Sow outdoors: May 7 – May 14
Squash & zucchini	Sow outdoors: May 7 – May 14
Basil	Start seeds indoors: Mar 19 – Apr 2 Transplant outdoors: May 7 – May 14

Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 15 (8 weeks before the average first fall frost on Oct 10).

Useful for zone 6a gardens

Seed starting kit with dome — to start seeds indoors before the last frost
LED grow light for seedlings — stops leggy seedlings
Frost cloth / plant covers — for late spring and early fall frosts
Soil thermometer — warm-season crops need soil above 60°F
Cold frame / mini greenhouse — adds weeks to a short season

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Frost risk in detail

	90% chance	50% chance	10% chance
Last 32°F frost in spring is after	Apr 19	Apr 30	May 10
First 32°F frost in fall is before	Oct 24	Oct 10	Sep 30

How to read it: in spring there is a 10% chance of a frost after May 10, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 30. A hard freeze (28°F) usually ends around April 18.

Hardiness zone by ZIP code in Westford

01886 zone 6a

Nearby cities

Chelmsford zone 6b, last frost Apr 30
Acton zone 6b, last frost May 2
Tyngsboro zone 6a, last frost Apr 30
Lowell zone 6b, last frost Apr 30
Maynard zone 6b, last frost May 2
Concord zone 6b, last frost Apr 28
Dracut zone 6a, last frost Apr 30
Billerica zone 6b, last frost Apr 27

All cities in Massachusetts → · Other zone 6a cities →

Questions

What growing zone is Westford, MA?

Westford is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map.

When is the last frost in Westford?

The average last spring frost (32°F) in Westford is April 30. There is still a 10% chance of frost until May 10.

When can I plant tomatoes in Westford?

Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 7 – May 14. Start seeds indoors 6–8 weeks before the last frost.

Frost dates: NOAA U.S. Climate Normals 1991–2020, station Lowell, MA (USC00194313), 9.2 km (5.7 mi) from the city center, elevation 34 m, based on 28 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.