Port Of Morgan, MT Frost Dates & Growing Season

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

Last spring frost
May 19
~50% chance of frost after
First fall frost
Sep 22
~50% chance of frost before
Growing season
126 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 5 May 19 Jun 2
First fall frost Oct 4 Sep 22 Sep 9
Hard freeze (28°F), median last May 8 · first Sep 30

Computed from NOAA 1991–2020 climate normals at the PORT OF MORGAN 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 Port Of Morgan

Computed from Port Of Morgan'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 24 – Apr 7 May 26 – Jun 2
🫑 Peppers Mar 10 – Mar 24 Jun 2 – Jun 9
🥬 Lettuce Apr 7 – Apr 21 Apr 21 – May 5 Apr 21 – May 19
🫛 Peas Apr 7 – Apr 21
🥕 Carrots Apr 28 – May 19
🥦 Broccoli Mar 31 – Apr 14 Apr 28 – May 12
🥬 Kale Apr 7 – Apr 21 Apr 21 – May 5 Apr 21 – May 5
🥒 Cucumbers Apr 21 – Apr 28 May 26 – Jun 2 May 26 – Jun 2
🥒 Zucchini Apr 21 – Apr 28 May 26 – Jun 2 May 26 – Jun 2
🫘 Green Beans (Bush) May 26 – Jun 2
🌽 Sweet Corn May 26 – Jun 2
🌿 Basil Apr 7 – Apr 21 May 26 – Jun 2 Jun 2 – Jun 9
🧄 Garlic Fall: Aug 11 – Sep 8

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 Port Of Morgan's dates automatically after a lookup.

Reading the season in Port Of Morgan

At about 126 frost-free days, Port Of Morgan 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 Port Of Morgan, MT?

The average last spring frost in Port Of Morgan is around May 19, 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 Port Of Morgan, MT?

The average first fall frost in Port Of Morgan arrives around Sep 22. 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 Port Of Morgan?

About 126 frost-free days on average, from May 19 to Sep 22. 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 Port Of Morgan 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.