Rogers Pass 9 NNE, MT Frost Dates & Growing Season

The two dates every Rogers Pass 9 NNE garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 21
~50% chance of frost after
First fall frost
Sep 15
~50% chance of frost before
Growing season
117 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 7 May 21 Jun 8
First fall frost Sep 29 Sep 15 Aug 30
Hard freeze (28°F), median last May 7 · first Sep 28

Computed from NOAA 1991–2020 climate normals at the ROGERS PASS 9 NNE 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 Rogers Pass 9 NNE

Computed from Rogers Pass 9 NNE'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 26 – Apr 9 May 28 – Jun 4
🫑 Peppers Mar 12 – Mar 26 Jun 4 – Jun 11
🥬 Lettuce Apr 9 – Apr 23 Apr 23 – May 7 Apr 23 – May 21
🫛 Peas Apr 9 – Apr 23
🥕 Carrots Apr 30 – May 21
🥦 Broccoli Apr 2 – Apr 16 Apr 30 – May 14
🥬 Kale Apr 9 – Apr 23 Apr 23 – May 7 Apr 23 – May 7
🥒 Cucumbers Apr 23 – Apr 30 May 28 – Jun 4 May 28 – Jun 4
🥒 Zucchini Apr 23 – Apr 30 May 28 – Jun 4 May 28 – Jun 4
🫘 Green Beans (Bush) May 28 – Jun 4
🌽 Sweet Corn May 28 – Jun 4
🌿 Basil Apr 9 – Apr 23 May 28 – Jun 4 Jun 4 – Jun 11
🧄 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 Rogers Pass 9 NNE's dates automatically after a lookup.

Reading the season in Rogers Pass 9 NNE

At about 117 frost-free days, Rogers Pass 9 NNE 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 Rogers Pass 9 NNE, MT?

The average last spring frost in Rogers Pass 9 NNE is around May 21, 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 Rogers Pass 9 NNE, MT?

The average first fall frost in Rogers Pass 9 NNE 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 Rogers Pass 9 NNE?

About 117 frost-free days on average, from May 21 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 Rogers Pass 9 NNE 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.