Green Mt Dam, CO Frost Dates & Growing Season

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

Last spring frost
Jun 6
~50% chance of frost after
First fall frost
Sep 14
~50% chance of frost before
Growing season
100 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 24 Jun 6 Jun 23
First fall frost Sep 26 Sep 14 Aug 31
Hard freeze (28°F), median last May 22 · first Sep 25

Computed from NOAA 1991–2020 climate normals at the GREEN MT DAM 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 Green Mt Dam

Computed from Green Mt Dam'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 11 – Apr 25 Jun 13 – Jun 20
🫑 Peppers Mar 28 – Apr 11 Jun 20 – Jun 27
🥬 Lettuce Apr 25 – May 9 May 9 – May 23 May 9 – Jun 6
🫛 Peas Apr 25 – May 9
🥕 Carrots May 16 – Jun 6
🥦 Broccoli Apr 18 – May 2 May 16 – May 30
🥬 Kale Apr 25 – May 9 May 9 – May 23 May 9 – May 23
🥒 Cucumbers May 9 – May 16 Jun 13 – Jun 20 Jun 13 – Jun 20
🥒 Zucchini May 9 – May 16 Jun 13 – Jun 20 Jun 13 – Jun 20
🫘 Green Beans (Bush) Jun 13 – Jun 20
🌽 Sweet Corn Jun 13 – Jun 20
🌿 Basil Apr 25 – May 9 Jun 13 – Jun 20 Jun 20 – Jun 27
🧄 Garlic Fall: Aug 3 – Aug 31

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 Green Mt Dam's dates automatically after a lookup.

Reading the season in Green Mt Dam

At about 100 frost-free days, Green Mt Dam 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 Green Mt Dam, CO?

The average last spring frost in Green Mt Dam is around Jun 6, 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 Green Mt Dam, CO?

The average first fall frost in Green Mt Dam arrives around Sep 14. 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 Green Mt Dam?

About 100 frost-free days on average, from Jun 6 to Sep 14. 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 Green Mt Dam 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.