USDA zone 5a in New Hampshire
USDA plant hardiness zone 5a covers 12 locations across New Hampshire (average annual extreme minimum −20 to −15 °F): Bristol, NH, Conway, NH, Conway, NH, Gorham, NH, Gorham, NH, Hanover, NH, and 6 more. Average last spring frost across this group ranges May 1 (Hanover) to May 24 (Lisbon), and growing seasons run 116–162 days (Lisbon to Hanover) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every New Hampshire location's own frost dates; the printable planting calendar uses Gorham, this group's median-season location.
- USDA zone
- 5a−20 to −15 °F
- Last frost range
- May 1–May 24avg, 32°F
- First frost range
- Sep 18–Oct 13avg, 32°F
- Growing season range
- 116–162days
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) |
|---|---|---|---|---|---|
| Bristol | Canaan | Grafton | May 21 | Sep 26 | 127 |
| Conway | Fryeburg, Kezar Falls | Fryeburg E Slopes Ap | May 17 | Sep 25 | 128 |
| Conway | Center Ossipee, Center Sandwich | Tamworth 4 | May 16 | Sep 26 | 129 |
| Gorham | Bethel | Berlin | May 14 | Sep 30 | 135 |
| Gorham * | Whitefield, Bartlett | Pinkham Notch | May 18 | Oct 1 | 135 |
| Hanover | Enfield, Wilder, Norwich, Hartford, South Royalton, Chelsea, +2 more | Hanover | May 1 | Oct 13 | 162 |
| Lebanon | Enfield, White River Junction, North Hartland, Plainfield | Lebanon Muni Ap | May 9 | Oct 6 | 148 |
| Lincoln | — | Lincoln Nepp | May 7 | Oct 4 | 149 |
| Lisbon | Lincoln, Bethlehem | Bethlehem 2 | May 24 | Sep 18 | 116 |
| Newport | Enfield | Newport | May 14 | Oct 1 | 140 |
| North Conway | Bartlett | N Conway | May 7 | Oct 5 | 150 |
| Plymouth | North Woodstock | Plymouth | May 20 | Sep 27 | 128 |
* Gorham 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 (Gorham, representative)
Computed from Gorham's average frost dates — the median-season location in this New Hampshirezone 5a 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 23 – Apr 6 | May 25 – Jun 1 | Jul 24 – Aug 13 | — | matures comfortably |
| Pepper | Very tender | Mar 9 – Mar 23 | Jun 1 – Jun 8 | Jul 31 – Aug 30 | — | matures comfortably |
| Cucumber | Tender | Apr 20 – Apr 27 | May 25 – Jun 1 | Jul 14 – Aug 3 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 25 – Jun 1 | Jul 9 – Jul 24 | — | matures comfortably |
| Bush bean | Tender | — | May 25 – Jun 1 | Jul 14 – Jul 24 | Aug 2 – Aug 12 | matures comfortably |
| Sweet corn | Tender | — | May 18 – Jun 1 | Jul 17 – Aug 16 | — | matures comfortably |
| Basil | Very tender | Apr 6 – Apr 20 | May 25 – Jun 1 | Jun 24 – Jul 9 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 6 – Apr 20 | Apr 20 – May 4 | Jun 4 – Jun 19 | Jul 19 – Aug 3 | matures comfortably |
| Pea | Hardy | — | Apr 6 – Apr 20 | May 31 – Jun 15 | Jul 9 – Jul 24 | matures comfortably |
| Spinach | Hardy | — | Apr 6 – Apr 20 | May 16 – May 26 | Jul 29 – Aug 8 | matures comfortably |
| Carrot | Half-hardy | — | Apr 27 – May 4 | Jun 26 – Jul 16 | Jun 29 – Jul 19 | matures comfortably |
| Broccoli | Half-hardy | Mar 23 – Apr 6 | Apr 20 – May 4 | Jun 14 – Jul 4 | Jul 4 – Jul 24 | matures comfortably |
Which crops fit this growing season
Using Gorham's own 135-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 (Gorham)
From NOAA's 1991–2020 Climate Normals at station USC00276818. 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 | Jun 1 | Jun 20 | Sep 19 | Oct 1 | 107 |
| 32°F (freeze) | May 18 | Jun 1 | Oct 1 | Oct 14 | 135 |
| 28°F | May 4 | May 20 | Oct 12 | Oct 28 | 160 |
| 24°F | Apr 22 | May 5 | Oct 25 | Nov 8 | 184 |
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 12 locations is 1,930; Gorham's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 1,475 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 3,147 | cool-season crops (brassicas, greens) |
Hardiness zone 5a in New Hampshire
Zone 5a means an average annual extreme minimum winter temperature of about −20 to −15 °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. New Hampshire spans 5 hardiness zones in this dataset — see all New Hampshire locations for the full range, including zones4a, 4b, 5b, 6a.
Explore zone 5a in other states at zone 5a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 5a mean in New Hampshire?
- Zone 5a means an average annual extreme minimum winter temperature of −20 to −15 °F — the standard USDA measure of which perennials survive winter. 12 locations in New Hampshire fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in New Hampshire's zone 5a is the growing season longest?
- Hanover runs the longest season on this page at about 162 days; Lisbon is shortest at about 116 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in New Hampshire's zone 5a?
- Using Gorham's frost dates (this page's median-season location): start seeds indoors about Mar 23 – Apr 6, then transplant outside about May 25 – Jun 1. 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 New Hampshire's zone 5a 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 12 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.