What does USDA hardiness zone 6a mean in Massachusetts?

Zone 6a means an average annual extreme minimum winter temperature of −10 to −5 °F — the standard USDA measure of which perennials survive winter. 15 locations in Massachusetts fall in this zone. It does not set planting dates; see the frost calendar below for that.

Where in Massachusetts's zone 6a is the growing season longest?

Methuen runs the longest season on this page at about 198 days; Northampton is shortest at about 144 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.

When should I plant tomatoes in Massachusetts's zone 6a?

Using Wilbraham's frost dates (this page's median-season location): start seeds indoors about Mar 12 – Mar 26, then transplant outside about May 14 – May 21. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Massachusetts's zone 6a have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 15 locations listed (see the table above for each location's own dates).

USDA zone 6a in Massachusetts

−10 to −5 °F avg. annual extreme minimum · 15 locations in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 6a covers 15 locations across Massachusetts (average annual extreme minimum −10 to −5 °F): Great Barrington, MA, Greenfield, MA, Haverhill, MA, Haverhill, MA, Leominster, MA, Littleton Common, MA, and 9 more. Average last spring frost across this group ranges April 13 (Methuen) to May 13 (Northampton), and growing seasons run 144–198 days (Northampton to Methuen) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Massachusetts location's own frost dates; the printable planting calendar uses Wilbraham, this group's median-season location.

USDA zone: 6a−10 to −5 °F
Last frost range: Apr 13–May 13avg, 32°F
First frost range: Oct 2–Oct 28avg, 32°F
Growing season range: 144–198days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Great Barrington	Chester	Lenox Dale	May 7	Oct 3	147
Greenfield	Deerfield	Greenfield #3	May 1	Oct 11	162
Haverhill	Derry, Amesbury	Haverhill	May 1	Oct 12	163
Haverhill	—	Groveland	May 3	Oct 8	158
Leominster	Fitchburg, Gardner, Devens, Lunenburg, Rutland, Townsend, +3 more	Fitchburg Muni Ap	Apr 29	Oct 11	164
Littleton Common	—	Maynard 2	May 2	Oct 6	156
Lowell	Littleton Common, Groton, East Pepperell	Lowell	Apr 30	Oct 10	164
Methuen	—	Lawrence	Apr 13	Oct 28	198
Northampton	Amherst, Ware, Belchertown, Granby, South Deerfield, Hatfield, +2 more	Amherst	May 5	Oct 8	156
Northampton	Huntington, Shelburne Falls, Chester	Worthington	May 13	Oct 2	144
Palmer	Ware, Wilbraham, Sturbridge, Monson Center, Fiskdale, Holland, +5 more	E Brimfield Lake	Apr 28	Oct 15	169
Turners Falls	Barre, Petersham, Millers Falls	Orange Muni Ap	May 4	Oct 8	157
Westfield	Northampton, Springfield, Chicopee, Holyoke, West Springfield, Easthampton, +3 more	Westfield Barnes Muni Ap	May 3	Oct 8	158
Wilbraham *	—	Staffordville	May 7	Oct 12	159
Worcester	Oxford, Northborough, Rutland, Spencer, Barre, Clinton, +1 more	Worcester Rgnl Ap	Apr 23	Oct 21	181

* Wilbraham is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Wilbraham, representative)

Computed from Wilbraham's average frost dates — the median-season location in this Massachusettszone 6a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Wilbraham (Massachusetts, zone 6a), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Mar 12 – Mar 26	May 14 – May 21	Jul 13 – Aug 2	—	matures comfortably
Pepper	Very tender	Feb 26 – Mar 12	May 21 – May 28	Jul 20 – Aug 19	—	matures comfortably
Cucumber	Tender	Apr 9 – Apr 16	May 14 – May 21	Jul 3 – Jul 23	—	matures comfortably
Summer squash / zucchini	Tender	—	May 14 – May 21	Jun 28 – Jul 13	—	matures comfortably
Bush bean	Tender	—	May 14 – May 21	Jul 3 – Jul 13	Aug 13 – Aug 23	matures comfortably
Sweet corn	Tender	—	May 7 – May 21	Jul 6 – Aug 5	—	matures comfortably
Basil	Very tender	Mar 26 – Apr 9	May 14 – May 21	Jun 13 – Jun 28	—	matures comfortably
Lettuce	Half-hardy	Mar 26 – Apr 9	Apr 9 – Apr 23	May 24 – Jun 8	Jul 30 – Aug 14	matures comfortably
Pea	Hardy	—	Mar 26 – Apr 9	May 20 – Jun 4	Jul 20 – Aug 4	matures comfortably
Spinach	Hardy	—	Mar 26 – Apr 9	May 5 – May 15	Aug 9 – Aug 19	matures comfortably
Carrot	Half-hardy	—	Apr 16 – Apr 23	Jun 15 – Jul 5	Jul 10 – Jul 30	matures comfortably
Broccoli	Half-hardy	Mar 12 – Mar 26	Apr 9 – Apr 23	Jun 3 – Jun 23	Jul 15 – Aug 4	matures comfortably

Which crops fit this growing season

Using Wilbraham's own 159-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Wilbraham)

From NOAA's 1991–2020 Climate Normals at station USC00067958. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Wilbraham.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	May 19	May 31	Oct 3	Oct 15	138
32°F (freeze)	May 7	May 21	Oct 12	Oct 27	159
28°F	Apr 25	May 11	Oct 24	Nov 7	182
24°F	Apr 9	Apr 28	Nov 5	Nov 22	209

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 15 locations is 2,598; Wilbraham's own reading is shown below.

Annual growing degree days for Wilbraham (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	2,310	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	4,309	cool-season crops (brassicas, greens)

Hardiness zone 6a in Massachusetts

Zone 6a means an average annual extreme minimum winter temperature of about −10 to −5 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Massachusetts spans 5 hardiness zones in this dataset — see all Massachusetts locations for the full range, including zones5b, 6b, 7a, 7b.

Explore zone 6a in other states at zone 6a, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 6a mean in Massachusetts?: Zone 6a means an average annual extreme minimum winter temperature of −10 to −5 °F — the standard USDA measure of which perennials survive winter. 15 locations in Massachusetts fall in this zone. It does not set planting dates; see the frost calendar below for that.
Where in Massachusetts's zone 6a is the growing season longest?: Methuen runs the longest season on this page at about 198 days; Northampton is shortest at about 144 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
When should I plant tomatoes in Massachusetts's zone 6a?: Using Wilbraham's frost dates (this page's median-season location): start seeds indoors about Mar 12 – Mar 26, then transplant outside about May 14 – May 21. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Massachusetts's zone 6a have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 15 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.