USDA Hardiness Zone 6a
Frost Dates for 03046 — Dunbarton, New Hampshire
NOAA 1991–2020 normals from Weare, NH (720 ft), 7 miles west.
Updated
In Dunbarton, the last spring frost (32°F) is around May 2 in half of years and has passed by May 14 in nine years out of ten. The first fall frost comes around October 8, as early as September 27 one year in ten, leaving a typical freeze-free season of 158 days (NOAA, Weare, NH).
- Last spring frost
- May 2
- First fall frost
- October 8
- Growing season
- 158 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°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 Dunbarton
Half of springs at Weare, NH see their last 32°F night by May 2; only one in ten is past it by April 22, and one in ten still has one after May 14. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 9 20%, and after May 14 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 88% of the 51 New Hampshire stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 8 in half of years, as early as September 27 one year in ten, and holds off past October 23 one year in ten. A hard freeze of 28°F follows 12 days later, around October 20; in spring the one-in-ten date for 28°F is May 2, 12 days before the 32°F one. The freeze-free season lasts 158 days in a typical year, longer than at 71% of the 51 New Hampshire stations; it reaches 174 days one year in ten and falls short of 139 one year in ten. On average 166 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 11 days longer, to about May 13, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 30 and March 20.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 1 | May 5 | May 8 | May 10 | May 13 | May 16 | May 20 | May 23 | May 27 |
| 32°F | Apr 22 | Apr 26 | Apr 28 | Apr 30 | May 2 | May 4 | May 6 | May 9 | May 14 |
| 28°F | Apr 10 | Apr 14 | Apr 17 | Apr 20 | Apr 21 | Apr 23 | Apr 26 | Apr 28 | May 2 |
| 24°F | Mar 29 | Apr 2 | Apr 4 | Apr 6 | Apr 9 | Apr 11 | Apr 14 | Apr 17 | Apr 20 |
| 20°F | Mar 15 | Mar 20 | Mar 25 | Mar 29 | Mar 31 | Apr 2 | Apr 4 | Apr 6 | Apr 10 |
| 16°F | Mar 7 | Mar 11 | Mar 14 | Mar 17 | Mar 20 | Mar 24 | Mar 28 | Mar 31 | Apr 3 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 11 |
| 32°F | Sep 27 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 18 | Oct 23 |
| 28°F | Oct 5 | Oct 10 | Oct 14 | Oct 18 | Oct 20 | Oct 24 | Oct 28 | Nov 1 | Nov 5 |
| 24°F | Oct 17 | Oct 23 | Oct 28 | Oct 31 | Nov 3 | Nov 6 | Nov 10 | Nov 14 | Nov 18 |
| 20°F | Nov 2 | Nov 7 | Nov 11 | Nov 14 | Nov 18 | Nov 21 | Nov 23 | Nov 27 | Dec 1 |
| 16°F | Nov 17 | Nov 22 | Nov 25 | Nov 28 | Nov 30 | Dec 1 | Dec 4 | Dec 8 | Dec 13 |
Freeze probabilities 1991–2020 at Weare, 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 03046 →Compare Dunbarton with another place →
Weather by month in Dunbarton
July is the warmest month at Weare, NH, averaging 80°F by day and 60°F at night; January is the coldest at 31°F and 13°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 56% of years.
Warmth for growing adds up to 2,251 growing degree days a year (base 50°F), more than at 51% of the 51 New Hampshire stations. 31% of them (689) have built up by the end of June, and July adds the most, 611.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 31 | 13 | 100% | 30 | 1 |
| Feb | 34 | 14 | 100% | 27 | 0 |
| Mar | 42 | 23 | 100% | 28 | 1 |
| Apr | 55 | 33 | 100% | 16 | 39 |
| May | 67 | 45 | 56% | 2 | 209 |
| Jun | 75 | 55 | 0% | <1 | 439 |
| Jul | 80 | 60 | 0% | 0 | 611 |
| Aug | 78 | 58 | 0% | 0 | 553 |
| Sep | 71 | 50 | 16% | 1 | 316 |
| Oct | 58 | 38 | 97% | 11 | 69 |
| Nov | 47 | 30 | 100% | 21 | 12 |
| Dec | 37 | 20 | 100% | 29 | 0 |
Monthly normals 1991–2020 at Weare, NH (720 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Weare 2 NE, NH, 8 miles west of Dunbarton, has a last frost 7 days later (May 9), a first frost 3 days earlier (October 5), a season 10 days shorter.
When it snows in Dunbarton, New Hampshire
The first measurable snow (0.1 inch or more) in Dunbarton 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 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 35 days after the last snow.
Planting calendar for 03046
| When | What to do |
|---|---|
| February 21 – March 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 7 – March 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 4 – April 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 2 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 8 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 03046 is 7 miles from Weare, NH, which stands at 720 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 03045 (Goffstown). The 2023 USDA Plant Hardiness Zone Map lists ZIP 03046 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°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.