Colebrook 3SW, NH Frost Dates & Growing Season

The two dates every Colebrook 3SW garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 31
~50% chance of frost after
First fall frost
Sep 21
~50% chance of frost before
Growing season
113 days
frost-free stretch
USDA zone
≈ 4b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost May 16 May 31 Jun 14
First fall frost Oct 2 Sep 21 Sep 7
Hard freeze (28°F), median last May 17 · first Oct 1

Computed from NOAA 1991–2020 climate normals at the COLEBROOK 3SW station. "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Colebrook 3SW

Computed from Colebrook 3SW's own frost dates. Click any crop for the full zone-4 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Apr 5 – Apr 19 Jun 7 – Jun 14
🫑 Peppers Mar 22 – Apr 5 Jun 14 – Jun 21
🥬 Lettuce Apr 19 – May 3 May 3 – May 17 May 3 – May 31
🫛 Peas Apr 19 – May 3
🥕 Carrots May 10 – May 31
🥦 Broccoli Apr 12 – Apr 26 May 10 – May 24
🥬 Kale Apr 19 – May 3 May 3 – May 17 May 3 – May 17
🥒 Cucumbers May 3 – May 10 Jun 7 – Jun 14 Jun 7 – Jun 14
🥒 Zucchini May 3 – May 10 Jun 7 – Jun 14 Jun 7 – Jun 14
🫘 Green Beans (Bush) Jun 7 – Jun 14
🌽 Sweet Corn Jun 7 – Jun 14
🌿 Basil Apr 19 – May 3 Jun 7 – Jun 14 Jun 14 – Jun 21
🧄 Garlic Fall: Aug 10 – Sep 7

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Colebrook 3SW's dates automatically after a lookup.

Reading the season in Colebrook 3SW

At about 113 frost-free days, Colebrook 3SW rewards efficiency: start warm-season crops indoors, favor short-season varieties, and lean on cold-tolerant crops — peas, kale, roots — that shrug off the shoulder-season frosts on either end.

Frequently asked questions

When is the last frost in Colebrook 3SW, NH?

The average last spring frost in Colebrook 3SW is around May 31, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Colebrook 3SW, NH?

The average first fall frost in Colebrook 3SW arrives around Sep 21. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Colebrook 3SW?

About 113 frost-free days on average, from May 31 to Sep 21. That favors short-season varieties and transplants for warm-season crops, with cool-season vegetables doing the heavy lifting in spring and fall.

What USDA zone is Colebrook 3SW in?

USDA zone 4b on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.