Caribou, ME Frost Dates & Growing Season

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

Last spring frost
May 7
~50% chance of frost after
First fall frost
Oct 1
~50% chance of frost before
Growing season
147 days
frost-free stretch
USDA zone
4a
2023 hardiness map
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 27 May 7 May 24
First fall frost Oct 14 Oct 1 Sep 17
Hard freeze (28°F), median last Apr 26 · first Oct 12

Computed from NOAA 1991–2020 climate normals at the Caribou Municipal Airport station (1 km from central Caribou). "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 Caribou

Computed from Caribou'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 Mar 12 – Mar 26 May 14 – May 21
🫑 Peppers Feb 26 – Mar 12 May 21 – May 28
🥬 Lettuce Mar 26 – Apr 9 Apr 9 – Apr 23 Apr 9 – May 7
🫛 Peas Mar 26 – Apr 9
🥕 Carrots Apr 16 – May 7
🥦 Broccoli Mar 19 – Apr 2 Apr 16 – Apr 30
🥬 Kale Mar 26 – Apr 9 Apr 9 – Apr 23 Apr 9 – Apr 23
🥒 Cucumbers Apr 9 – Apr 16 May 14 – May 21 May 14 – May 21
🥒 Zucchini Apr 9 – Apr 16 May 14 – May 21 May 14 – May 21
🫘 Green Beans (Bush) May 14 – May 21
🌽 Sweet Corn May 14 – May 21
🌿 Basil Mar 26 – Apr 9 May 14 – May 21 May 21 – May 28
🧄 Garlic Fall: Aug 20 – Sep 17

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 Caribou's dates automatically after a lookup.

Reading the season in Caribou

At about 147 frost-free days, Caribou 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 Caribou, ME?

The average last spring frost in Caribou is around May 7, 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 Caribou, ME?

The average first fall frost in Caribou arrives around Oct 1. 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 Caribou?

About 147 frost-free days on average, from May 7 to Oct 1. 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 Caribou in?

USDA zone 4a 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.