Heart Mtn, WY Frost Dates & Growing Season

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

Last spring frost
May 15
~50% chance of frost after
First fall frost
Sep 25
~50% chance of frost before
Growing season
133 days
frost-free stretch
USDA zone
≈ 5a
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost May 1 May 15 Jun 1
First fall frost Oct 10 Sep 25 Sep 11
Hard freeze (28°F), median last May 2 · first Oct 6

Computed from NOAA 1991–2020 climate normals at the HEART MTN 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 Heart Mtn

Computed from Heart Mtn'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 Mar 20 – Apr 3 May 22 – May 29
🫑 Peppers Mar 6 – Mar 20 May 29 – Jun 5
🥬 Lettuce Apr 3 – Apr 17 Apr 17 – May 1 Apr 17 – May 15
🫛 Peas Apr 3 – Apr 17
🥕 Carrots Apr 24 – May 15
🥦 Broccoli Mar 27 – Apr 10 Apr 24 – May 8
🥬 Kale Apr 3 – Apr 17 Apr 17 – May 1 Apr 17 – May 1
🥒 Cucumbers Apr 17 – Apr 24 May 22 – May 29 May 22 – May 29
🥒 Zucchini Apr 17 – Apr 24 May 22 – May 29 May 22 – May 29
🫘 Green Beans (Bush) May 22 – May 29
🌽 Sweet Corn May 22 – May 29
🌿 Basil Apr 3 – Apr 17 May 22 – May 29 May 29 – Jun 5
🧄 Garlic Fall: Aug 14 – Sep 11

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 Heart Mtn's dates automatically after a lookup.

Reading the season in Heart Mtn

At about 133 frost-free days, Heart Mtn 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 Heart Mtn, WY?

The average last spring frost in Heart Mtn is around May 15, 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 Heart Mtn, WY?

The average first fall frost in Heart Mtn arrives around Sep 25. 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 Heart Mtn?

About 133 frost-free days on average, from May 15 to Sep 25. 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 Heart Mtn in?

USDA zone 5a 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.