USDA zone 7a in Maine
USDA plant hardiness zone 7a covers 1 location across Maine (average annual extreme minimum 0 to 5 °F): Thomaston, ME. Average last spring frost across this group ranges April 27 and growing seasons run 178 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Maine location's own frost dates; the printable planting calendar uses Thomaston, this group's median-season location.
- USDA zone
- 7a0 to 5 °F
- Last frost range
- Apr 27avg, 32°F
- First frost range
- Oct 25avg, 32°F
- Growing season range
- 178days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Thomaston * | — | Tenants Harbor | Apr 27 | Oct 25 | 178 |
* Thomaston is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Thomaston, representative)
Computed from Thomaston's average frost dates — the median-season location in this Mainezone 7a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Mar 2 – Mar 16 | May 4 – May 11 | Jul 3 – Jul 23 | — | matures comfortably |
| Pepper | Very tender | Feb 16 – Mar 2 | May 11 – May 18 | Jul 10 – Aug 9 | — | matures comfortably |
| Cucumber | Tender | Mar 30 – Apr 6 | May 4 – May 11 | Jun 23 – Jul 13 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 4 – May 11 | Jun 18 – Jul 3 | — | matures comfortably |
| Bush bean | Tender | — | May 4 – May 11 | Jun 23 – Jul 3 | Aug 26 – Sep 5 | matures comfortably |
| Sweet corn | Tender | — | Apr 27 – May 11 | Jun 26 – Jul 26 | — | matures comfortably |
| Basil | Very tender | Mar 16 – Mar 30 | May 4 – May 11 | Jun 3 – Jun 18 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 16 – Mar 30 | Mar 30 – Apr 13 | May 14 – May 29 | Aug 12 – Aug 27 | matures comfortably |
| Pea | Hardy | — | Mar 16 – Mar 30 | May 10 – May 25 | Aug 2 – Aug 17 | matures comfortably |
| Spinach | Hardy | — | Mar 16 – Mar 30 | Apr 25 – May 5 | Aug 22 – Sep 1 | matures comfortably |
| Carrot | Half-hardy | — | Apr 6 – Apr 13 | Jun 5 – Jun 25 | Jul 23 – Aug 12 | matures comfortably |
| Broccoli | Half-hardy | Mar 2 – Mar 16 | Mar 30 – Apr 13 | May 24 – Jun 13 | Jul 28 – Aug 17 | matures comfortably |
Which crops fit this growing season
Using Thomaston's own 178-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Thomaston)
From NOAA's 1991–2020 Climate Normals at station USC00176881. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 9 | May 24 | Oct 11 | Oct 25 | 153 |
| 32°F (freeze) | Apr 27 | May 8 | Oct 25 | Nov 6 | 178 |
| 28°F | Apr 14 | Apr 24 | Nov 6 | Nov 19 | 205 |
| 24°F | Apr 2 | Apr 15 | Nov 19 | Dec 1 | 230 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 1 locations is 1,712; Thomaston's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 1,712 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 3,696 | cool-season crops (brassicas, greens) |
Hardiness zone 7a in Maine
Zone 7a means an average annual extreme minimum winter temperature of about 0 to 5 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Maine spans 8 hardiness zones in this dataset — see all Maine locations for the full range, including zones3b, 4a, 4b, 5a, 5b, 6a, 6b.
Explore zone 7a in other states at zone 7a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 7a mean in Maine?
- Zone 7a means an average annual extreme minimum winter temperature of 0 to 5 °F — the standard USDA measure of which perennials survive winter. 1 location in Maine fall in this zone. It does not set planting dates; see the frost calendar below for that.
- When should I plant tomatoes in Maine's zone 7a?
- Using Thomaston's frost dates (this page's median-season location): start seeds indoors about Mar 2 – Mar 16, then transplant outside about May 4 – May 11. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Maine's zone 7a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.