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Frost dates for Plymouth, NH

NOAA weather station USC00276945 at 660 ft elevation. Based on 17 years within 1991-2020. Last verified 2026-10-17.

Last spring freeze (32°F)

May 20

median: freeze still happened after this date in half of years

May 26 30% risk · Jun 4 10% risk

First fall freeze (32°F)

Sep 27

median: a freeze had happened by this date in half of years

Sep 14 10% chance of a freeze earlier than this

Freeze-free season

128 days

median length between last spring and first fall 32°F freeze

How to read these dates

Spring: a "10% risk" date means NOAA's 1991-2020 data put the chance of a 32°F or colder night after that date at 10%. The "30% risk" date is the convention used by some popular frost calculators (the Old Farmer's Almanac says it uses a 30% probability threshold, source). Fall: a "10%" date means a 10% chance the first freeze comes before it. Source: NOAA readme.

Full table for this station

ThresholdSpring: latest-freeze date at risk of 10% / 30% / 50%Fall: first-freeze date at chance of 10% / 50%
36°F (frost possible)Jun 13 / Jun 5 / May 31Sep 1 / Sep 15
32°F (freeze)Jun 4 / May 26 / May 20Sep 14 / Sep 27
28°F (hard freeze)May 24 / May 14 / May 7Sep 24 / Oct 6

Also at 32°F, last-freeze 70% date May 14 and 90% date May 6 (frost still likely after these early dates). Data quality: Representative: 10+ years of qualifying data, missing months filled from nearby stations. Source: NOAA NCEI U.S. Climate Normals 1991-2020, station USC00276945, read 2026-10-17.

Is Memorial Day safe here?

Many New England gardeners wait for Memorial Day (it falls between May 25 and May 31). At this station, NOAA's chance of a 32°F or colder night after May 25 is 30-50%, and after May 31 is 10-30%. Your own spot may differ. See all stations.

UNH Extension says that for central New Hampshire, Memorial Day is a conservative estimate of the last frost date (read 2026-10-17).

Your planting schedule

Pick how cautious you want to be. The dates apply UNH Extension's per-crop rules (UNH fact sheet, read 2026-10-17) to this station's last-freeze date. UNH's sheet does not say which probability its "last frost" means, so you choose. These are planning dates, not instructions; follow your seed packet and the weather.

Last-frost reference date

Showing the schedule for the 2027 season (dates repeat yearly). Table below defaults to Typical; it updates when you choose.

CropStart seeds indoorsOutdoorsUNH Extension rule used
SpinachMar 3 – Apr 7Set out Apr 14 – May 5Start 4-6 wk before set-out; set out 3-6 wk before last frost.
BroccoliMar 17 – Apr 14Set out Apr 28 – May 12Start 4-6 wk before set-out; set out 2-4 wk before last frost.
Brussels sproutMar 17 – Apr 14Set out Apr 28 – May 12Start 4-6 wk before set-out; set out 2-4 wk before last frost.
CabbageMar 17 – Mar 31Set out Apr 28Start 4-6 wk before set-out; set out 4 wk before last frost.
KaleMar 17 – Mar 31Set out Apr 28Start 4-6 wk before set-out; set out 4 wk before last frost.
KohlrabiMar 17 – Mar 31Set out Apr 28Start 4-6 wk before set-out; set out 4 wk before last frost.
LeekFeb 17 – Mar 3Set out Apr 28Start 8-10 wk before set-out; set out 4 wk before last frost.
LettuceMar 24 – Apr 7Set out Apr 28 – May 5Start 4-5 wk before set-out; set out 3-4 wk before last frost.
OnionFeb 17 – Mar 3Set out Apr 28Start 8-10 wk before set-out; set out 4 wk before last frost.
Radish—Sow Apr 28 – May 12Sow seed in garden 2-4 wk before last frost.
Turnip—Sow Apr 28 – May 12Sow seed in garden 2-4 wk before last frost.
ParsleyFeb 24 – Mar 10Set out May 5 – May 12Start 9-10 wk before set-out; set out 2-3 wk before last frost.
CauliflowerMar 31 – Apr 14Set out May 12Start 4-6 wk before set-out; set out 2 wk before last frost.
Potato—Sow May 12 – May 19Plant seed potatoes 1-2 wk before last frost.
Swiss chardMar 31 – Apr 14Set out May 12; or sow Apr 28Start 4-6 wk before set-out; set out 2 wk before last frost; or sow seed 4 wk before last frost.
Bean—Sow on/after May 26Sow seed in garden after last frost.
CeleryMar 3 – Mar 17Set out on/after May 26Start 10-12 wk before set-out; set out after last frost.
Parsnip—Sow on/after May 26Sow seed in garden after last frost.
CucumberMay 5 – May 19Set out Jun 2 – Jun 9
Direct sow when soil reaches 70°F		Start 3-4 wk before set-out; set out 1-2 wk after last frost; or sow when soil warms to 70°F.
Sweet potato—Plant slips Jun 2 – Jun 9Plant slips (young plants) 1-2 wk after last frost.
TomatoApr 7 – Apr 28Set out Jun 2 – Jun 9Start 6-8 wk before set-out; set out 1-2 wk after last frost.
BasilApr 14 – Apr 28Set out Jun 9Start 6-8 wk before set-out; set out 2 wk after last frost.
EggplantMar 31 – Apr 21Set out Jun 9 – Jun 16Start 8-10 wk before set-out; set out 2-3 wk after last frost.
MelonMay 12 – May 19Set out Jun 9Start 3-4 wk before set-out; set out 2 wk after last frost.
PepperMar 31 – Apr 14Set out Jun 9Start 8-10 wk before set-out; set out 2 wk after last frost.
PumpkinMay 12 – May 19Set out Jun 9
Direct sow when soil reaches 70°F		Start 3-4 wk before set-out; set out 2 wk after last frost; or sow when soil warms to 70°F.
Summer squashMay 12 – May 19Set out Jun 9
Direct sow when soil reaches 70°F		Start 3-4 wk before set-out; set out 2 wk after last frost; or sow when soil warms to 70°F.
Winter squashMay 12 – May 19Set out Jun 9
Direct sow when soil reaches 70°F		Start 3-4 wk before set-out; set out 2 wk after last frost; or sow when soil warms to 70°F.
ZucchiniMay 12 – May 19Set out Jun 9
Direct sow when soil reaches 70°F		Start 3-4 wk before set-out; set out 2 wk after last frost; or sow when soil warms to 70°F.
Rutabaga—Sow Jun 15 – Jul 15Sow seed in garden mid-June to mid-July (fixed dates, not tied to frost).
Beet—Sow when soil reaches 45°F (use a soil thermometer)Sow seed in garden when soil warms to 45°F.
Carrot—Sow when soil reaches 60°F (use a soil thermometer)Sow seed in garden when soil warms to 60°F.
Corn—Sow when soil reaches 60°F (use a soil thermometer)Sow seed in garden when soil warms to 60°F.
Pea—Sow as soon as soil thawsSow seed in garden as soon as soil thaws.

Fall: when the garden ends

At this station the median first 32°F freeze is Sep 27; there is a 10% chance of one before Sep 14. Tender crops (tomatoes, peppers, basil) can be damaged at 33-36°F (Almanac.com notes some plants are damaged in that range); the 36°F first-frost date here is median Sep 15 and 10% date Sep 1. UNH Extension notes many fall vegetables tolerate mild frosts down to about 28°F (median first 28°F here: Oct 6), and that row covers can extend the season. UNH: Fall vegetable gardening, read 2026-10-17.

Your garden is not the weather station

This station sits at 660 ft. UNH Extension says first-freeze dates vary "even between relatively close locations, based on factors such as elevation" (source), and notes that gardeners who keep garden journals can use their own records. Gardeners on Reddit describe the same thing: elevation and cold spots change when they can plant (for example r/vermont). Treat these dates as a starting point.

Nearby stations