USDA hardiness zones in Maine
| Zone | Avg. extreme minimum | ZIP codes | Example cities |
|---|---|---|---|
| Zone 3b | −35 to −30°F | 1 | — |
| Zone 4a | −30 to −25°F | 23 | Presque Isle, Caribou |
| Zone 4b | −25 to −20°F | 24 | — |
| Zone 5a | −20 to −15°F | 135 | Bangor, Brewer, Old Town |
| Zone 5b | −15 to −10°F | 122 | Lewiston, Auburn, Sanford, Westbrook |
| Zone 6a | −10 to −5°F | 86 | Portland, South Portland, Biddeford, Saco |
| Zone 6b | −5 to 0°F | 9 | — |
| Zone 7a | 0 to 5°F | 1 | — |
Growing zone and frost dates by city
| City | Zone | Frost dates |
|---|---|---|
| Portland | 6a (−10 to −5°F) | Portland frost dates |
| Lewiston | 5b (−15 to −10°F) | Lewiston frost dates |
| Bangor | 5a (−20 to −15°F) | Bangor frost dates |
| South Portland | 6a (−10 to −5°F) | South Portland frost dates |
| Auburn | 5b (−15 to −10°F) | Auburn frost dates |
| Sanford | 5b (−15 to −10°F) | Sanford frost dates |
| Biddeford | 6a (−10 to −5°F) | Biddeford frost dates |
| Westbrook | 5b (−15 to −10°F) | Westbrook frost dates |
| Saco | 6a (−10 to −5°F) | Saco frost dates |
| Augusta | 5b (−15 to −10°F) | Augusta frost dates |
| Waterville | 5b (−15 to −10°F) | Waterville frost dates |
| Brewer | 5a (−20 to −15°F) | Brewer frost dates |
| Ellsworth | 5b (−15 to −10°F) | Ellsworth frost dates |
| Bath | 6a (−10 to −5°F) | Bath frost dates |
| Presque Isle | 4a (−30 to −25°F) | Presque Isle frost dates |
| Old Town | 5a (−20 to −15°F) | Old Town frost dates |
| Caribou | 4a (−30 to −25°F) | Caribou frost dates |
| Rockland | 6a (−10 to −5°F) | Rockland frost dates |
| Belfast | 5b (−15 to −10°F) | Belfast frost dates |
| Gardiner | 5b (−15 to −10°F) | Gardiner frost dates |
Frequently asked questions
What growing zone is Maine in?
Maine’s ZIP codes span USDA zones 3b to 7a, and 5a is the most common. Zones vary with elevation and distance from water, so check your own ZIP code.
When should I plant?
Hardiness zones are about winter cold, not planting dates. For timing, use the last spring frost date for your city on our Maine frost dates page.