USDA zone 5b in New Hampshire
USDA plant hardiness zone 5b covers 14 locations across New Hampshire (average annual extreme minimum −15 to −10 °F): Claremont, NH, Concord, NH, Franklin, NH, Franklin, NH, Franklin, NH, Henniker, NH, and 8 more. Average last spring frost across this group ranges April 30 (Franklin) to May 20 (Plymouth), and growing seasons run 128–170 days (Plymouth to Franklin) — 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 Henniker, this group's median-season location.
- USDA zone
- 5b−15 to −10 °F
- Last frost range
- Apr 30–May 20avg, 32°F
- First frost range
- Sep 26–Oct 18avg, 32°F
- Growing season range
- 128–170days
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) |
|---|---|---|---|---|---|
| Claremont | Windsor, Charlestown, Blodgett Landing | Newport | May 14 | Oct 1 | 140 |
| Concord | Contoocook, Loudon, Pittsfield | Concord Muni Ap | May 8 | Oct 3 | 146 |
| Franklin | — | Franklin Falls Dam | May 7 | Oct 3 | 148 |
| Franklin | Laconia, Wolfeboro, Bristol, Tilton Northfield, Meredith, Pittsfield, +4 more | Lakeport 2 | Apr 30 | Oct 18 | 170 |
| Franklin | — | Salisbury | May 14 | Sep 29 | 138 |
| Henniker * | — | Hopkinton Lake | May 6 | Oct 1 | 146 |
| Jaffrey | Bennington | Jaffrey Muni Ap | May 5 | Oct 6 | 152 |
| Keene | Brattleboro, West Swanzey, Hinsdale, West Brattleboro, Putney, Walpole, +5 more | Keene | May 14 | Oct 1 | 138 |
| Melvin | Suissevale, Center Ossipee, Center Sandwich | Tamworth 4 | May 16 | Sep 26 | 129 |
| Milton | — | Rochester Skyhaven Ap | Apr 30 | Oct 9 | 161 |
| New London | Warner, Bradford, Blodgett Landing | Mt Sunapee | May 2 | Oct 9 | 158 |
| North Conway | — | N Conway | May 7 | Oct 5 | 150 |
| North Woodstock | — | Benton 5 Sw | May 15 | Sep 28 | 133 |
| Plymouth | Bristol, Ashland | Plymouth | May 20 | Sep 27 | 128 |
* Henniker 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 (Henniker, representative)
Computed from Henniker's average frost dates — the median-season location in this New Hampshirezone 5b 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 11 – Mar 25 | May 13 – May 20 | Jul 12 – Aug 1 | — | matures comfortably |
| Pepper | Very tender | Feb 25 – Mar 11 | May 20 – May 27 | Jul 19 – Aug 18 | — | matures comfortably |
| Cucumber | Tender | Apr 8 – Apr 15 | May 13 – May 20 | Jul 2 – Jul 22 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 13 – May 20 | Jun 27 – Jul 12 | — | matures comfortably |
| Bush bean | Tender | — | May 13 – May 20 | Jul 2 – Jul 12 | Aug 2 – Aug 12 | matures comfortably |
| Sweet corn | Tender | — | May 6 – May 20 | Jul 5 – Aug 4 | — | matures comfortably |
| Basil | Very tender | Mar 25 – Apr 8 | May 13 – May 20 | Jun 12 – Jun 27 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 25 – Apr 8 | Apr 8 – Apr 22 | May 23 – Jun 7 | Jul 19 – Aug 3 | matures comfortably |
| Pea | Hardy | — | Mar 25 – Apr 8 | May 19 – Jun 3 | Jul 9 – Jul 24 | matures comfortably |
| Spinach | Hardy | — | Mar 25 – Apr 8 | May 4 – May 14 | Jul 29 – Aug 8 | matures comfortably |
| Carrot | Half-hardy | — | Apr 15 – Apr 22 | Jun 14 – Jul 4 | Jun 29 – Jul 19 | matures comfortably |
| Broccoli | Half-hardy | Mar 11 – Mar 25 | Apr 8 – Apr 22 | Jun 2 – Jun 22 | Jul 4 – Jul 24 | matures comfortably |
Which crops fit this growing season
Using Henniker's own 146-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 (Henniker)
From NOAA's 1991–2020 Climate Normals at station USC00274218. 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 20 | Jun 3 | Sep 23 | Oct 4 | 125 |
| 32°F (freeze) | May 6 | May 20 | Oct 1 | Oct 13 | 146 |
| 28°F | Apr 27 | May 8 | Oct 11 | Oct 28 | 166 |
| 24°F | Apr 15 | Apr 28 | Oct 25 | Nov 8 | 190 |
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 14 locations is 2,193; Henniker's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,294 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,219 | cool-season crops (brassicas, greens) |
Hardiness zone 5b in New Hampshire
Zone 5b means an average annual extreme minimum winter temperature of about −15 to −10 °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, 5a, 6a.
Explore zone 5b in other states at zone 5b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 5b mean in New Hampshire?
- Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 14 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 5b is the growing season longest?
- Franklin runs the longest season on this page at about 170 days; Plymouth is shortest at about 128 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 5b?
- Using Henniker's frost dates (this page's median-season location): start seeds indoors about Mar 11 – Mar 25, then transplant outside about May 13 – May 20. 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 5b 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 14 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.