USDA Hardiness Zone 5b
Frost Dates for 03242 — Henniker, New Hampshire
NOAA 1991–2020 normals from Hopkinton Lake, NH (430 ft), 4 miles east.
Updated
In Henniker, the last spring frost (32°F) is around May 6 in half of years and has passed by May 20 in nine years out of ten. The first fall frost comes around October 1, as early as September 20 one year in ten, leaving a typical freeze-free season of 146 days (NOAA, Hopkinton Lake, NH).
- Last spring frost
- May 6
- First fall frost
- October 1
- Growing season
- 146 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- November 18
- Last snow
- March 28
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
15 of 15 observed
NOAA normal
Frost risk by date in Henniker
Half of springs at Hopkinton Lake, NH see their last 32°F night by May 6; only one in ten is past it by April 27, and one in ten still has one after May 20. Planting tender crops after May 12 leaves a 30% risk of a frost on them, after May 16 20%, and after May 20 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 25% of the 51 New Hampshire stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 1 in half of years, as early as September 20 one year in ten, and holds off past October 13 one year in ten. A hard freeze of 28°F follows 10 days later, around October 11; in spring the one-in-ten date for 28°F is May 8, 12 days before the 32°F one. The freeze-free season lasts 146 days in a typical year, shorter than at 61% of the 51 New Hampshire stations; it reaches 162 days one year in ten and falls short of 128 one year in ten. On average 171 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about May 20, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 18 and March 27.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 6 | May 10 | May 14 | May 17 | May 20 | May 23 | May 26 | May 30 | Jun 3 |
| 32°F | Apr 27 | Apr 30 | May 2 | May 4 | May 6 | May 9 | May 12 | May 16 | May 20 |
| 28°F | Apr 17 | Apr 21 | Apr 23 | Apr 25 | Apr 27 | Apr 30 | May 1 | May 4 | May 8 |
| 24°F | Apr 4 | Apr 7 | Apr 10 | Apr 13 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 |
| 20°F | Mar 23 | Mar 30 | Apr 1 | Apr 3 | Apr 4 | Apr 6 | Apr 9 | Apr 13 | Apr 17 |
| 16°F | Mar 13 | Mar 16 | Mar 20 | Mar 23 | Mar 27 | Mar 30 | Apr 1 | Apr 3 | Apr 6 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 10 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 1 | Oct 4 |
| 32°F | Sep 20 | Sep 24 | Sep 28 | Sep 30 | Oct 1 | Oct 3 | Oct 6 | Oct 9 | Oct 13 |
| 28°F | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 28 |
| 24°F | Oct 8 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 28 | Nov 1 | Nov 4 | Nov 8 |
| 20°F | Oct 22 | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 21 |
| 16°F | Nov 2 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 22 | Nov 25 | Nov 30 | Dec 4 |
Freeze probabilities 1991–2020 at Hopkinton Lake, NH, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 03242 →Compare Henniker with another place →
Compared with the next station
The nearest other station, Weare 2 NE, NH, 6 miles southeast of Henniker and 375 feet higher, has a last frost 3 days later (May 9), a first frost 4 days later (October 5), a season 2 days longer.
When it snows in Henniker, New Hampshire
The first measurable snow (0.1 inch or more) in Henniker usually arrives around November 18, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Weare, NH, 7.3 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 39 days after the last snow.
Planting calendar for 03242
| When | What to do |
|---|---|
| February 25 – March 11 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 11 – March 25 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 8 – April 22 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 6 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 9 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 17 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 1 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 03242 is 4 miles from Hopkinton Lake, NH, which stands at 430 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 03242 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across New Hampshire →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.