USDA hardiness zones — 2023 map
Maine hardiness zones — USDA planting zone map + what to grow
Zones 3b-6a · most of Maine is zone 5a · Northeast region
MaineUSDA zone range & map
On the 2023 USDA Plant Hardiness Zone Map, Maine spans zones 3b-6a. The map shades the state from the far north Aroostook County interior (zone 3b) through to the southern coast around Portland (zone 6a). The single most common half-zone across the populated state is zone 5a — that is the figure to use if you only remember one number for Maine. Maine is a short-season cold-climate state, milder along the coast and noticeably colder in the northern and mountain interior.
| USDA zone range | Zones 3b-6a |
|---|---|
| Most common zone | Zone 5a |
| Coldest area | the far north Aroostook County interior (zone 3b) |
| Warmest area | the southern coast around Portland (zone 6a) |
| Average last spring frost | mid-May |
| Average first fall frost | late September |
Source: USDA 2023 Plant Hardiness Zone Map (1991-2020 normals). Frost averages: NOAA/NCEI 1991-2020 climate normals. Local ZIP-level zones and frost dates can differ from these statewide figures.
Maine hardiness zones by major city
Zones shift across Maine with elevation and distance from the coast. Here is the 2023 USDA half-zone for the largest cities:
| City | USDA zone |
|---|---|
| Portland | Zone 6a |
| Bangor | Zone 5a |
| Augusta | Zone 5b |
| Presque Isle | Zone 4a |
Need your exact zone? Run the ZIP-code zone finder for a precise half-zone and frost dates for your address.
ZIP-code zones in Maine
Statewide ranges hide a lot. Tap your area for its exact USDA half-zone, last and first frost dates, and what to plant now:
- Biddeford 04005 — Zone 5b
- Portland 04101 — Zone 6a
- Portland (Deering) 04102 — Zone 6a
- South Portland 04106 — Zone 6a
- Lewiston 04240 — Zone 5b
- Augusta 04330 — Zone 5b
- Bangor 04401 — Zone 5a
- Waterville 04901 — Zone 5a
What Maine's zone range means for planting
Your hardiness zone tells you which perennials, shrubs, and trees will survive a typical Maine winter, and it anchors when tender crops can go outside. Because Maine spans 3b-6a, two gardeners in the same state can have very different planting calendars.
- Pick perennials hardy to your local zone. Across most of Maine that means at least zone 5a; gardeners in the far north Aroostook County interior (zone 3b) should choose hardier plants.
- Anchor tender crops to your frost dates. With a last spring frost around mid-May and first fall frost around late September, set out tomatoes, peppers, and basil after the last frost and protect them before the first.
- Adjust for your microclimate. Urban heat, a south-facing slope, or a cold valley pocket can shift your effective zone and frost dates by a half-zone or more from the statewide figure.
Find your exact zone in Maine
The 3b-6a range is statewide. Growli pins your hardiness zone and frost dates to your exact ZIP code and sends a push notification before any forecast frost night for your saved location.
Frequently asked questions
What hardiness zone is Maine?
Maine spans USDA hardiness zones 3b-6a on the 2023 USDA Plant Hardiness Zone Map. The most common zone — covering the largest share of the populated state — is zone 5a. The coldest areas are the far north Aroostook County interior (zone 3b) and the warmest are the southern coast around Portland (zone 6a).
When is the last frost in Maine?
Across most of Maine the average last spring frost falls around mid-May and the first fall frost around late September. These are statewide averages — colder, higher areas run later in spring and earlier in fall, so check a ZIP-level estimate for your exact spot.
What grows well in Maine?
Maine is a short-season cold-climate state, milder along the coast and noticeably colder in the northern and mountain interior. Match plants to your local half-zone within the 3b-6a range: choose varieties hardy to at least zone 5a for reliable overwintering, and time tender crops around your local frost dates. The zone 5 planting guide lists vegetables, fruit, and ornamentals suited to most of the state.
Why does Maine have more than one hardiness zone?
Hardiness zones track the average annual coldest temperature, which changes with latitude, elevation, distance from water, and urban heat. That is why Maine ranges from the far north Aroostook County interior (zone 3b) to the southern coast around Portland (zone 6a) — a span of 3b-6a — even though it is a single state.
Did Maine's hardiness zone change in 2023?
The USDA updated the Plant Hardiness Zone Map in November 2023 using 1991-2020 climate data. About half the country, including parts of Maine, shifted to the next warmer half-zone versus the 2012 map. The 3b-6a range here reflects the current 2023 map. Always confirm your address against the official USDA map for plant-survival decisions.