Simpson 6 N - Wildhorse, MT Frost Dates & Growing Season

The two dates every Simpson 6 N - Wildhorse garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 26
~50% chance of frost after
First fall frost
Sep 15
~50% chance of frost before
Growing season
112 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 12 May 26 Jun 8
First fall frost Sep 25 Sep 15 Sep 1
Hard freeze (28°F), median last May 14 · first Sep 23

Computed from NOAA 1991–2020 climate normals at the SIMPSON 6 N - WILDHORSE 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 Simpson 6 N - Wildhorse

Computed from Simpson 6 N - Wildhorse'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 31 – Apr 14 Jun 2 – Jun 9
🫑 Peppers Mar 17 – Mar 31 Jun 9 – Jun 16
🥬 Lettuce Apr 14 – Apr 28 Apr 28 – May 12 Apr 28 – May 26
🫛 Peas Apr 14 – Apr 28
🥕 Carrots May 5 – May 26
🥦 Broccoli Apr 7 – Apr 21 May 5 – May 19
🥬 Kale Apr 14 – Apr 28 Apr 28 – May 12 Apr 28 – May 12
🥒 Cucumbers Apr 28 – May 5 Jun 2 – Jun 9 Jun 2 – Jun 9
🥒 Zucchini Apr 28 – May 5 Jun 2 – Jun 9 Jun 2 – Jun 9
🫘 Green Beans (Bush) Jun 2 – Jun 9
🌽 Sweet Corn Jun 2 – Jun 9
🌿 Basil Apr 14 – Apr 28 Jun 2 – Jun 9 Jun 9 – Jun 16
🧄 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 Simpson 6 N - Wildhorse's dates automatically after a lookup.

Reading the season in Simpson 6 N - Wildhorse

At about 112 frost-free days, Simpson 6 N - Wildhorse 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 Simpson 6 N - Wildhorse, MT?

The average last spring frost in Simpson 6 N - Wildhorse is around May 26, 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 Simpson 6 N - Wildhorse, MT?

The average first fall frost in Simpson 6 N - Wildhorse 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 Simpson 6 N - Wildhorse?

About 112 frost-free days on average, from May 26 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 Simpson 6 N - Wildhorse 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.