Mizpah 4 NNW, MT Frost Dates & Growing Season

The two dates every Mizpah 4 NNW garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 22
~50% chance of frost after
First fall frost
Sep 15
~50% chance of frost before
Growing season
116 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 9 May 22 Jun 7
First fall frost Oct 1 Sep 15 Sep 2
Hard freeze (28°F), median last May 11 · first Sep 25

Computed from NOAA 1991–2020 climate normals at the MIZPAH 4 NNW 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 Mizpah 4 NNW

Computed from Mizpah 4 NNW'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 27 – Apr 10 May 29 – Jun 5
🫑 Peppers Mar 13 – Mar 27 Jun 5 – Jun 12
🥬 Lettuce Apr 10 – Apr 24 Apr 24 – May 8 Apr 24 – May 22
🫛 Peas Apr 10 – Apr 24
🥕 Carrots May 1 – May 22
🥦 Broccoli Apr 3 – Apr 17 May 1 – May 15
🥬 Kale Apr 10 – Apr 24 Apr 24 – May 8 Apr 24 – May 8
🥒 Cucumbers Apr 24 – May 1 May 29 – Jun 5 May 29 – Jun 5
🥒 Zucchini Apr 24 – May 1 May 29 – Jun 5 May 29 – Jun 5
🫘 Green Beans (Bush) May 29 – Jun 5
🌽 Sweet Corn May 29 – Jun 5
🌿 Basil Apr 10 – Apr 24 May 29 – Jun 5 Jun 5 – Jun 12
🧄 Garlic Fall: Aug 4 – Sep 1

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 Mizpah 4 NNW's dates automatically after a lookup.

Reading the season in Mizpah 4 NNW

At about 116 frost-free days, Mizpah 4 NNW 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 Mizpah 4 NNW, MT?

The average last spring frost in Mizpah 4 NNW is around May 22, 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 Mizpah 4 NNW, MT?

The average first fall frost in Mizpah 4 NNW arrives around Sep 15. 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 Mizpah 4 NNW?

About 116 frost-free days on average, from May 22 to Sep 15. 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 Mizpah 4 NNW 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.