Maine Planting Zones
Maine runs from zone 3b to zone 7a on the 2023 USDA map. Zone 5a is the most common, covering 32% of the state's ZIP codes. Portland is 6a, Bangor is 5a and Presque Isle is 4a.
Zones across Maine
| Zone | Average coldest night | Share of Maine ZIP codes |
|---|---|---|
| 3b | −35 to −30°F | under 1% |
| 4a | −30 to −25°F | 5% |
| 4b | −25 to −20°F | 6% |
| 5a | −20 to −15°F | 32% |
| 5b | −15 to −10°F | 31% |
| 6a | −10 to −5°F | 23% |
| 6b | −5 to 0°F | 2% |
| 7a | 0 to 5°F | under 1% |
Planting zone for every city and town in Maine
Each Maine town uses the ZIP code at its center. Big towns can cross into the next half-zone, so look up your own ZIP if you're near a line.
| City | Zone | Average coldest night |
|---|---|---|
| Auburn | 5b | −15 to −10°F |
| Augusta | 5b | −15 to −10°F |
| Bangor | 5a | −20 to −15°F |
| Bath | 6a | −10 to −5°F |
| Belfast | 5b | −15 to −10°F |
| Brewer | 5a | −20 to −15°F |
| Calais | 5b | −15 to −10°F |
| Caribou | 4a | −30 to −25°F |
| Eastport | 6a | −10 to −5°F |
| Ellsworth | 5b | −15 to −10°F |
| Gardiner | 5b | −15 to −10°F |
| Hallowell | 5b | −15 to −10°F |
| Lewiston | 5b | −15 to −10°F |
| Old Town | 5a | −20 to −15°F |
| Portland | 6a | −10 to −5°F |
| Presque Isle | 4a | −30 to −25°F |
| Rockland | 6a | −10 to −5°F |
| Saco | 6a | −10 to −5°F |
| Sanford | 5b | −15 to −10°F |
| South Portland | 6a | −10 to −5°F |
| Waterville | 5b | −15 to −10°F |
| Westbrook | 5b | −15 to −10°F |
Source: USDA Plant Hardiness Zone Map, 2023, Agricultural Research Service, U.S. Department of Agriculture; ZIP code table from the PRISM Group, Oregon State University (accessed Oct 2026). This list is our own summary, not the official USDA map. See how we calculate.
Frequently asked questions
What planting zone is Maine?
Maine spans zones 3b to 7a on the 2023 USDA map, and zone 5a is the most common. Look up your ZIP code for your exact zone.
What zone is Portland, ME?
Portland is zone 6a, where the coldest night of an average winter falls from −10 to −5°F. Plants rated hardy to zone 6 or colder should survive a typical winter there.
More for Maine: Maine climate zones (insulation) · Last frost dates in Maine · Frost line depth by state