Butte Bert Mooney Airport, MT Frost Dates & Growing Season

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

Last spring frost
Jun 13
~50% chance of frost after
First fall frost
Sep 5
~50% chance of frost before
Growing season
84 days
frost-free stretch
USDA zone
≈ 5b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost May 27 Jun 13 Jul 1
First fall frost Sep 19 Sep 5 Aug 24
Hard freeze (28°F), median last May 21 · first Sep 17

Computed from NOAA 1991–2020 climate normals at the BUTTE BERT MOONEY AP 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 Butte Bert Mooney Airport

Computed from Butte Bert Mooney Airport's own frost dates. Click any crop for the full zone-5 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Apr 18 – May 2 Jun 20 – Jun 27
🫑 Peppers Apr 4 – Apr 18 Jun 27 – Jul 4
🥬 Lettuce May 2 – May 16 May 16 – May 30 May 16 – Jun 13
🫛 Peas May 2 – May 16
🥕 Carrots May 23 – Jun 13
🥦 Broccoli Apr 25 – May 9 May 23 – Jun 6
🥬 Kale May 2 – May 16 May 16 – May 30 May 16 – May 30
🥒 Cucumbers May 16 – May 23 Jun 20 – Jun 27 Jun 20 – Jun 27
🥒 Zucchini May 16 – May 23 Jun 20 – Jun 27 Jun 20 – Jun 27
🫘 Green Beans (Bush) Jun 20 – Jun 27
🌽 Sweet Corn Jun 20 – Jun 27
🌿 Basil May 2 – May 16 Jun 20 – Jun 27 Jun 27 – Jul 4
🧄 Garlic Fall: Jul 25 – Aug 22

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 Butte Bert Mooney Airport's dates automatically after a lookup.

Reading the season in Butte Bert Mooney Airport

At about 84 frost-free days, Butte Bert Mooney Airport 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 Butte Bert Mooney Airport, MT?

The average last spring frost in Butte Bert Mooney Airport is around Jun 13, 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 Butte Bert Mooney Airport, MT?

The average first fall frost in Butte Bert Mooney Airport arrives around Sep 5. 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 Butte Bert Mooney Airport?

About 84 frost-free days on average, from Jun 13 to Sep 5. 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 Butte Bert Mooney Airport in?

USDA zone 5b 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.