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Home Garden Lot: Garden & Home Improvement

What Hardiness Zone Is Maine?

USDA 2023 Plant Hardiness Zone Map · 478 ZIP codes · Data updated 2026-10-28

Quick answer

Maine spans USDA hardiness zones 3b–7a on the 2023 Plant Hardiness Zone Map. The most common zone is 5a, covering 32% of Maine's ZIP codes, followed by zone 5b (31%). Zone 5a means the coldest night of an average winter reaches −20°F to −15°F (−29°C to −26°C). Enter your ZIP code for your exact zone.

Maine hardiness zones by share of ZIP codes

Zone 3b<1% · 1 ZIP
Zone 4a5% · 26 ZIPs
Zone 4b6% · 30 ZIPs
Zone 5a32% · 151 ZIPs
Zone 5b31% · 150 ZIPs
Zone 6a23% · 109 ZIPs
Zone 6b2% · 10 ZIPs
Zone 7a<1% · 1 ZIP

What the zones mean for Maine gardeners

  • Coldest and warmest towns: among towns with NOAA weather stations, Clayton Lake (1,000 ft) is in zone 3b, while Kennebunkport (20 ft) is in zone 6a. That is a difference of about 25°F in the coldest night of a typical winter.
  • Same zone, different frost dates: within zone 5a, the median last spring frost ranges from May 1 at Orono to May 17 at Millinocket Wastewater, 16 days apart. Your zone tells you which perennials survive winter; your frost dates tell you when to plant.

Typical frost dates in each Maine zone

Medians across NOAA weather stations in each zone. Colder zones usually have later spring frosts, but local terrain can shift the dates by weeks.

ZoneLast spring frostFirst fall frostStations
4aMay 20September 256
4bMay 19September 2511
5aMay 10October 220
5bMay 3October 1023
6aApril 28October 1910

Hardiness zones for Maine cities

Zones at the National Weather Service stations, mostly city airports, with their median frost dates.
Augusta State Airport5b−15°F to −10°F350Apr 27Oct 16
Bangor Intl Airport5a−20°F to −15°F148May 4Oct 4
Brunswick NAS5b−15°F to −10°F70May 2Oct 10
Caribou Municipal Airport4a−30°F to −25°F624May 7Oct 1
Frenchville Aroostook Airport4b−25°F to −20°F988May 6Oct 2
Fryeburg E Slopes Airport5a−20°F to −15°F445May 17Sep 25
Greenville Maine Forestry Svc4b−25°F to −20°F1,037May 7Oct 9
Limestone 4 NNW4a−30°F to −25°F737May 16Sep 24
Old Town 2 W5a−20°F to −15°F127May 13Sep 28
Portland Intl Jetport6a−10°F to −5°F45Apr 26Oct 15
Wiscasset Airport5b−15°F to −10°F68May 8Oct 7

Hardiness zones for 71 towns in Maine

Each NOAA weather station is shown with the USDA zone of the nearest ZIP code (within 8 miles). Coldest night is the zone's range for the average annual extreme minimum temperature. Click a column to sort.
Acadia National Park6a−10°F to −5°F470Apr 27Oct 22
Allagash4b−25°F to −20°F596Jun 2Sep 15
Andover 24b−25°F to −20°F822May 19Sep 25
Augusta State Airport5b−15°F to −10°F350Apr 27Oct 16
Bangor Intl Airport5a−20°F to −15°F148May 4Oct 4
Barnard5a−20°F to −15°F545May 12Oct 1
Bath6a−10°F to −5°F25May 10Oct 6
Belfast5b−15°F to −10°F20May 7Oct 5
Bethel 6 SSE5a−20°F to −15°F790May 6Oct 2
Brassua Dam4b−25°F to −20°F1,069May 23Sep 29
Bridgewater4a−30°F to −25°F420May 25Sep 18
Bridgton 3 NW5a−20°F to −15°F508May 5Oct 5
Brunswick NAS5b−15°F to −10°F70May 2Oct 10
Cape Neddick6a−10°F to −5°F152May 1Oct 14
Caribou Municipal Airport4a−30°F to −25°F624May 7Oct 1
Clayton Lake3b−35°F to −30°F1,000May 30Sep 13
Corinna4b−25°F to −20°F297May 8Oct 3
Danforth4b−25°F to −20°F475May 25Sep 24
Dover-foxcroft Wwtp5a−20°F to −15°F370May 15Sep 28
Durham5b−15°F to −10°F140May 15Oct 2
E Sangerville5a−20°F to −15°F635May 6Oct 7
E Surry5b−15°F to −10°F105May 8Oct 9
East Hiram5a−20°F to −15°F528May 12Oct 1
Eastport6a−10°F to −5°F85Apr 29Oct 25
Farmington5a−20°F to −15°F405May 16Sep 26
Fort Kent4a−30°F to −25°F610May 23Sep 24
Frenchville Aroostook Airport4b−25°F to −20°F988May 6Oct 2
Fryeburg E Slopes Airport5a−20°F to −15°F445May 17Sep 25
Gardiner5b−15°F to −10°F133May 1Oct 11
Grand Lake Stream5b−15°F to −10°F290May 4Oct 10
Gray6a−10°F to −5°F378Apr 28Oct 19
Greenville Maine Forestry Svc4b−25°F to −20°F1,037May 7Oct 9
Harmony5a−20°F to −15°F320May 11Oct 1
Hartford5b−15°F to −10°F705May 6Oct 3
Hollis5b−15°F to −10°F304May 14Sep 30
Houlton 5N4b−25°F to −20°F390May 19Sep 23
Jackman4b−25°F to −20°F1,214May 26Sep 23
Jonesboro5b−15°F to −10°F194May 3Oct 9
Kennebunkport6a−10°F to −5°F20May 9Oct 3
Lewiston5b−15°F to −10°F180Apr 25Oct 19
Limestone 4 NNW4a−30°F to −25°F737May 16Sep 24
Lincoln Sanitary District/wtp5a−20°F to −15°F190May 4Oct 6
Livermore Falls 1 E5b−15°F to −10°F380May 11Sep 29
Long Falls Dam4b−25°F to −20°F1,160May 13Sep 30
Madison5a−20°F to −15°F220May 8Oct 5
Millinocket Wastewater5a−20°F to −15°F360May 17Sep 29
New Sharon5a−20°F to −15°F480May 7Oct 2
Newcastle5b−15°F to −10°F213Apr 27Oct 18
Old Town 2 W5a−20°F to −15°F127May 13Sep 28
Orono5a−20°F to −15°F115May 1Oct 6
Poland5b−15°F to −10°F570May 3Oct 7
Portland Intl Jetport6a−10°F to −5°F45Apr 26Oct 15
Presque Isle4a−30°F to −25°F599May 14Sep 26
Rangeley 2 NW4b−25°F to −20°F1,780May 23Sep 24
Robbinston5b−15°F to −10°F115May 5Oct 13
Rumford 1 SSE5a−20°F to −15°F630May 4Oct 6
Rumford 6SW5a−20°F to −15°F630May 12Sep 29
Sanford 2 NNW5b−15°F to −10°F289May 16Sep 30
Tenants Harbor6a−10°F to −5°F21Apr 27Oct 25
Topsfield 25a−20°F to −15°F620May 6Oct 8
Turner5b−15°F to −10°F565May 1Oct 10
Van Buren 24a−30°F to −25°F456May 23Sep 26
Vanceboro No 25a−20°F to −15°F420May 13Oct 1
W Rockport 1 NNW6a−10°F to −5°F361Apr 27Oct 19
Waterville Trtmt Plt5b−15°F to −10°F73May 2Oct 10
Wesley5b−15°F to −10°F410May 2Oct 15
West Buxton 2 NNW5b−15°F to −10°F220May 7Oct 4
Westport Island6a−10°F to −5°F90Apr 28Oct 21
Windham 2NW5b−15°F to −10°F443Apr 30Oct 20
Wiscasset Airport5b−15°F to −10°F68May 8Oct 7
Woodland5b−15°F to −10°F123Apr 21Oct 26

Frequently asked questions

What hardiness zone is Maine?

Maine is in USDA hardiness zones 3b–7a on the 2023 USDA Plant Hardiness Zone Map. Zone 5a is the most common, covering 32% of Maine's ZIP codes, and zone 5b covers 31%. Enter your ZIP code for your exact zone.

What does zone 5a mean?

Zone 5a means the average annual extreme minimum temperature, the coldest night of a typical winter, is −20°F to −15°F (−29°C to −26°C). Perennials, shrubs and trees rated for zone 5a or colder should survive winter there.

What is the coldest hardiness zone in Maine?

Zone 3b is the coldest zone mapped in Maine, found around Clayton Lake, and zone 7a is the warmest.

Did Maine's hardiness zones change in 2023?

The USDA released a new Plant Hardiness Zone Map in November 2023, based on 1991–2020 temperatures instead of 1976–2005. About half of the United States shifted half a zone warmer. Check your ZIP code here, because plant tags and older books may still list your 2012 zone.

When should I plant in zone 5a?

Hardiness zones don't set planting dates; frost dates do. Inside zone 5a in Maine, the median last spring frost varies from May 1 to May 17. Look up your local frost dates and plant tender crops such as tomatoes after the 10%-risk last-frost date.

Zone and frost dates: use both

Your hardiness zone answers one question: will this plant survive the winter here? Choose perennials, shrubs, trees and bulbs rated for your zone or a colder one. For vegetables and annuals, what matters is the length of the frost-free season. See Maine frost dates by town, or get a planting calendar for your ZIP code with start-indoors, transplant and sowing dates for 30 crops.

Sources and method

Zones are from the USDA 2023 Plant Hardiness Zone Map ZIP-code files published by the PRISM Climate Group, Oregon State University, based on 1991–2020 minimum temperatures. ZIP codes are assigned to states by USPS prefix. Town zones use the ZIP code nearest each NOAA 1991–2020 Climate Normals station. This is an independent tool, not an official USDA site. Full methodology.

Hardiness zones in other states