USDA Hardiness Zone 5b
Frost Dates for 03431 — Keene, New Hampshire
NOAA 1991–2020 normals from Keene, NH (511 ft), 2 miles west.
Updated
In Keene, the last spring frost (32°F) is around May 14 in half of years and has passed by May 28 in nine years out of ten. The first fall frost comes around October 1, as early as September 18 one year in ten, leaving a typical freeze-free season of 138 days (NOAA, Keene, NH).
- Last spring frost
- May 14
- First fall frost
- October 1
- Growing season
- 138 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 24
- Last snow
- April 3
- Winters with snow
- 100%
- Snow per year
- 59.8"
median, 1991–2020
median, 1991–2020
27 of 27 observed
NOAA normal
Frost risk by date in Keene
Half of springs at Keene, NH see their last 32°F night by May 14; only one in ten is past it by April 30, and one in ten still has one after May 28. Planting tender crops after May 19 leaves a 30% risk of a frost on them, after May 23 20%, and after May 28 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 18 one year in ten, and holds off past October 14 one year in ten. A hard freeze of 28°F follows 9 days later, around October 10; in spring the one-in-ten date for 28°F is May 16, 12 days before the 32°F one. The freeze-free season lasts 138 days in a typical year, shorter than at 71% of the 51 New Hampshire stations; it reaches 156 days one year in ten and falls short of 119 one year in ten. On average 174 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 13 days longer, to about May 27, and return around September 21. Severe cold of 16°F or below comes every winter, usually between November 20 and March 29.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 13 | May 17 | May 21 | May 24 | May 27 | May 30 | Jun 1 | Jun 4 | Jun 9 |
| 32°F | Apr 30 | May 4 | May 8 | May 11 | May 14 | May 16 | May 19 | May 23 | May 28 |
| 28°F | Apr 21 | Apr 25 | Apr 28 | Apr 30 | May 2 | May 5 | May 8 | May 11 | May 16 |
| 24°F | Apr 6 | Apr 11 | Apr 16 | Apr 19 | Apr 21 | Apr 24 | Apr 26 | Apr 30 | May 5 |
| 20°F | Mar 25 | Mar 31 | Apr 2 | Apr 4 | Apr 6 | Apr 8 | Apr 11 | Apr 15 | Apr 19 |
| 16°F | Mar 13 | Mar 18 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 1 | Apr 4 | Apr 7 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 7 | Sep 11 | Sep 15 | Sep 18 | Sep 21 | Sep 23 | Sep 27 | Sep 30 | Oct 4 |
| 32°F | Sep 18 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 5 | Oct 9 | Oct 14 |
| 28°F | Sep 29 | Oct 2 | Oct 5 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 20 | Oct 25 |
| 24°F | Oct 7 | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 27 | Oct 31 | Nov 2 | Nov 9 |
| 20°F | Oct 19 | Oct 26 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 16 | Nov 21 |
| 16°F | Nov 4 | Nov 9 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Dec 1 | Dec 5 |
Freeze probabilities 1991–2020 at Keene, 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 03431 →Compare Keene with another place →
Weather by month in Keene
July is the warmest month at Keene, NH, averaging 82°F by day and 56°F at night; January is the coldest at 30°F and 10°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 89% of years.
Warmth for growing adds up to 2,165 growing degree days a year (base 50°F), fewer than at 63% of the 51 New Hampshire stations. 30% of them (642) have built up by the end of June, and July adds the most, 587. Precipitation totals 46.3 inches a year, most in October (4.9") and least in February (2.8"); May to September bring 46% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 30 | 10 | 3.1 | 100% | 30 | 0 |
| Feb | 34 | 11 | 2.8 | 100% | 27 | 0 |
| Mar | 43 | 20 | 3.4 | 100% | 28 | 4 |
| Apr | 57 | 30 | 3.4 | 100% | 19 | 37 |
| May | 69 | 41 | 3.8 | 89% | 5 | 186 |
| Jun | 77 | 51 | 4.4 | 4% | <1 | 415 |
| Jul | 82 | 56 | 4.5 | 0% | 0 | 587 |
| Aug | 81 | 54 | 4.3 | 0% | 0 | 541 |
| Sep | 73 | 47 | 4.3 | 46% | 1 | 313 |
| Oct | 60 | 36 | 4.9 | 100% | 13 | 73 |
| Nov | 47 | 27 | 3.5 | 100% | 23 | 8 |
| Dec | 36 | 18 | 3.9 | 100% | 29 | 0 |
Monthly normals 1991–2020 at Keene, NH (511 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, Walpole 2S Nepp, NH, 10 miles northwest of Keene, has a last frost 6 days earlier (May 8), a first frost 2 days later (October 3), a season 11 days longer.
When it snows in Keene, New Hampshire
The first measurable snow (0.1 inch or more) in Keene usually arrives around November 24, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Keene, NH, 2 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 41 days after the last snow.
Planting calendar for 03431
| When | What to do |
|---|---|
| March 5 – March 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 19 – April 2 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 16 – April 30 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 14 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 03431 is 2 miles from Keene, NH, which stands at 511 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 03431 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.