Maine Planting Zones by City and ZIP Code
Maine runs from zones 3b to 7a; 32% of its ZIPs are 5a, Portland is 6a and Bangor is 5a.
Maine runs from zones 3b to 7a
The coldest night of the winter averages -35°F to -30°F in the coldest of Maine’s ZIP codes and 0°F to 5°F in the warmest. Most of the state is zone 5a.
Planting zones of Maine cities
| City | Zone | Coldest night, on average | Since 2012 |
|---|---|---|---|
| Portland04101 | 6a | -10°F to -5°F | half a zone warmer than 2012 (5b) |
| Bangor04401 | 5a | -20°F to -15°F | same as 2012 |
| Augusta04330 | 5b | -15°F to -10°F | half a zone warmer than 2012 (5a) |
| Caribou04736 | 4a | -30°F to -25°F | half a zone colder than 2012 (4b) |
| Bar Harbor04609 | 6a | -10°F to -5°F | half a zone warmer than 2012 (5b) |
| Lewiston04240 | 5b | -15°F to -10°F | same as 2012 |
Tap a ZIP for that address’s frost dates and this month’s jobs.
Find your zone anywhere in Maine
A ZIP code or a town gives you its zone, how it moved since 2012, the frost dates at the nearest NOAA station, and the jobs for this month timed from them.
What to plant in Maine this month
The calendar for each of Maine's main zones, from vegetables to pruning and winter protection, each job tied to the extension page it comes from. Pick a month, or read the whole year below it.
Timed from the median frost dates of the 21 NOAA stations in Maine’s zone 5a: last spring frost May 8, first fall frost Oct 1. Your own ZIP’s frost dates move every window, so the ZIP tool times them for you.
Pick a month above to see every job in it.
The year at a glance
- Start vegetable seeds indoorsJan to May
- Sow vegetables in the gardenApr to May
- Sow the fall vegetable gardenJun to Aug
- Set out transplantsApr to May
- Plant trees and shrubsMar 27 to May 22 and Sep 17 to Nov 5
- Plant garlicSep 17 to Oct 22
- Plant tulips and other spring bulbsOct 8 to Oct 15
- Divide fall-blooming perennialsApr 17 to May 29
- Divide spring and summer-blooming perennialsAug 20 to Oct 1
- Prune trees and summer-flowering shrubs while dormantFeb 27 to Apr 10
- Prune spring-flowering shrubs after they bloomApr 24 to Jun 19
- Water evergreens and new plantings until the ground freezesSep 3 to Nov 12
- Mulch perennial crowns once the ground freezesNov 12 to Nov 26
- Pull back the winter mulchMar 20 to Apr 3
- Put hardware cloth around young tree trunksOct 1 to Nov 12
- Dig and store canna, dahlia and gladiolusOct 1 to Oct 8
- Cut back perennials after a hard freezeOct 8 to Nov 5
What changed in Maine since 2012
Every ZIP on both mapsCompared ZIP by ZIP from the 2023 and 2012 USDA tables; 478 Maine ZIP codes appear in both.
Why Maine’s zones moved
Of the cities above, Portland went from 5b to 6a, Augusta went from 5a to 5b, Caribou went from 4b to 4a and Bar Harbor went from 5b to 6a.
The USDA explains the national picture: “When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone.” The new map uses 1991 to 2020 and more than 13,000 weather stations, so it draws Maine’s hills, valleys and cities more finely than the 2012 map did.
A warmer zone changes which perennials and shrubs come through the winter, not when the garden gets planted; that still follows the frost dates.
Frost dates and seed starting in Maine
Maine planting zone questions
Planting zones by state
Sources. USDA Plant Hardiness Zone Map, ZIP code tables (2023 and 2012), PRISM Climate Group, Oregon State University; USDA Plant Hardiness Zone Map; USDA Unveils Updated Plant Hardiness Zone Map (USDA Agricultural Research Service, November 15, 2023); NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1); NC State Extension Gardener Plant Toolbox. Zones are read from the PRISM ZIP code tables, read Oct 9, 2026; a ZIP code’s zone is the zone at its center. The calendar’s extension sources are listed on the planting zones page and under each job.