What does USDA hardiness zone 3b mean in Maine?

Zone 3b means an average annual extreme minimum winter temperature of −35 to −30 °F — the standard USDA measure of which perennials survive winter. 1 location in Maine fall in this zone. It does not set planting dates; see the frost calendar below for that.

When should I plant tomatoes in Maine's zone 3b?

Using Eagle Lake's frost dates (this page's median-season location): start seeds indoors about Apr 4 – Apr 18, then transplant outside about Jun 6 – Jun 13. 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 Maine's zone 3b 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 1 locations listed (see the table above for each location's own dates).

USDA zone 3b in Maine

−35 to −30 °F avg. annual extreme minimum · 1 location in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 3b covers 1 location across Maine (average annual extreme minimum −35 to −30 °F): Eagle Lake, ME. Average last spring frost across this group ranges May 30 and growing seasons run 106 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Maine location's own frost dates; the printable planting calendar uses Eagle Lake, this group's median-season location.

USDA zone: 3b−35 to −30 °F
Last frost range: May 30avg, 32°F
First frost range: Sep 13avg, 32°F
Growing season range: 106days

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)
Eagle Lake *	—	Clayton Lake	May 30	Sep 13	106

* Eagle Lake 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 (Eagle Lake, representative)

Computed from Eagle Lake's average frost dates — the median-season location in this Mainezone 3b 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 Eagle Lake (Maine, zone 3b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Apr 4 – Apr 18	Jun 6 – Jun 13	Aug 5 – Aug 25	—	matures comfortably
Pepper	Very tender	Mar 21 – Apr 4	Jun 13 – Jun 20	Aug 12 – Sep 11	—	matures, but with little margin
Cucumber	Tender	May 2 – May 9	Jun 6 – Jun 13	Jul 26 – Aug 15	—	matures comfortably
Summer squash / zucchini	Tender	—	Jun 6 – Jun 13	Jul 21 – Aug 5	—	matures comfortably
Bush bean	Tender	—	Jun 6 – Jun 13	Jul 26 – Aug 5	Jul 15 – Jul 25	matures comfortably
Sweet corn	Tender	—	May 30 – Jun 13	Jul 29 – Aug 28	—	matures comfortably
Basil	Very tender	Apr 18 – May 2	Jun 6 – Jun 13	Jul 6 – Jul 21	—	matures comfortably
Lettuce	Half-hardy	Apr 18 – May 2	May 2 – May 16	Jun 16 – Jul 1	Jul 1 – Jul 16	matures comfortably
Pea	Hardy	—	Apr 18 – May 2	Jun 12 – Jun 27	Jun 21 – Jul 6	matures comfortably
Spinach	Hardy	—	Apr 18 – May 2	May 28 – Jun 7	Jul 11 – Jul 21	matures comfortably
Carrot	Half-hardy	—	May 9 – May 16	Jul 8 – Jul 28	Jun 11 – Jul 1	matures comfortably
Broccoli	Half-hardy	Apr 4 – Apr 18	May 2 – May 16	Jun 26 – Jul 16	Jun 16 – Jul 6	matures comfortably

Which crops fit this growing season

Using Eagle Lake's own 106-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 11 of 12 crops mature here with comfortable margin, 1matures with little room to spare. The tightest fits: pepper (+2 day 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 (Eagle Lake)

From NOAA's 1991–2020 Climate Normals at station USC00171472. 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), Eagle Lake.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	—	—	—	—	81
32°F (freeze)	May 30	Jun 12	Sep 13	Sep 27	106
28°F	May 13	May 31	Sep 27	Oct 11	134
24°F	Apr 30	May 14	Oct 10	Oct 29	160

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 1 locations is 1,353; Eagle Lake's own reading is shown below.

Annual growing degree days for Eagle Lake (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	1,353	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	2,880	cool-season crops (brassicas, greens)

Hardiness zone 3b in Maine

Zone 3b means an average annual extreme minimum winter temperature of about −35 to −30 °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. Maine spans 8 hardiness zones in this dataset — see all Maine locations for the full range, including zones4a, 4b, 5a, 5b, 6a, 6b, 7a.

Explore zone 3b in other states at zone 3b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 3b mean in Maine?: Zone 3b means an average annual extreme minimum winter temperature of −35 to −30 °F — the standard USDA measure of which perennials survive winter. 1 location in Maine fall in this zone. It does not set planting dates; see the frost calendar below for that.
When should I plant tomatoes in Maine's zone 3b?: Using Eagle Lake's frost dates (this page's median-season location): start seeds indoors about Apr 4 – Apr 18, then transplant outside about Jun 6 – Jun 13. 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 Maine's zone 3b 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 1 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.