Duluth, MN Frost Dates & Growing Season

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

Last spring frost
May 14
~50% chance of frost after
First fall frost
Oct 12
~50% chance of frost before
Growing season
151 days
frost-free stretch
USDA zone
4b
2023 hardiness map
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 24 May 14 Jun 1
First fall frost Oct 26 Oct 12 Sep 25
Hard freeze (28°F), median last Apr 29 · first Oct 25

Computed from NOAA 1991–2020 climate normals at the Duluth Harbor Stn station (3 km from central Duluth). "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 Duluth

Computed from Duluth'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 19 – Apr 2 May 21 – May 28
🫑 Peppers Mar 5 – Mar 19 May 28 – Jun 4
🥬 Lettuce Apr 2 – Apr 16 Apr 16 – Apr 30 Apr 16 – May 14
🫛 Peas Apr 2 – Apr 16
🥕 Carrots Apr 23 – May 14
🥦 Broccoli Mar 26 – Apr 9 Apr 23 – May 7
🥬 Kale Apr 2 – Apr 16 Apr 16 – Apr 30 Apr 16 – Apr 30
🥒 Cucumbers Apr 16 – Apr 23 May 21 – May 28 May 21 – May 28
🥒 Zucchini Apr 16 – Apr 23 May 21 – May 28 May 21 – May 28
🫘 Green Beans (Bush) May 21 – May 28
🌽 Sweet Corn May 21 – May 28
🌿 Basil Apr 2 – Apr 16 May 21 – May 28 May 28 – Jun 4
🧄 Garlic Fall: Aug 31 – Sep 28

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 Duluth's dates automatically after a lookup.

Reading the season in Duluth

Roughly 151 frost-free days gives Duluth gardeners room for nearly every common vegetable. Warm-season crops go out after May 14; a fall garden sown in late summer matures comfortably before the Oct 12 frost.

Frequently asked questions

When is the last frost in Duluth, MN?

The average last spring frost in Duluth is around May 14, 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 Duluth, MN?

The average first fall frost in Duluth arrives around Oct 12. 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 Duluth?

About 151 frost-free days on average, from May 14 to Oct 12. That fits nearly all common vegetables, though the longest-season melons and sweet potatoes benefit from transplants.

What USDA zone is Duluth 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.