Manassa, CO Frost Dates & Growing Season

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

Last spring frost
May 28
~50% chance of frost after
First fall frost
Sep 21
~50% chance of frost before
Growing season
116 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 13 May 28 Jun 11
First fall frost Oct 1 Sep 21 Sep 9
Hard freeze (28°F), median last May 13 · first Sep 29

Computed from NOAA 1991–2020 climate normals at the MANASSA 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 Manassa

Computed from Manassa'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 2 – Apr 16 Jun 4 – Jun 11
🫑 Peppers Mar 19 – Apr 2 Jun 11 – Jun 18
🥬 Lettuce Apr 16 – Apr 30 Apr 30 – May 14 Apr 30 – May 28
🫛 Peas Apr 16 – Apr 30
🥕 Carrots May 7 – May 28
🥦 Broccoli Apr 9 – Apr 23 May 7 – May 21
🥬 Kale Apr 16 – Apr 30 Apr 30 – May 14 Apr 30 – May 14
🥒 Cucumbers Apr 30 – May 7 Jun 4 – Jun 11 Jun 4 – Jun 11
🥒 Zucchini Apr 30 – May 7 Jun 4 – Jun 11 Jun 4 – Jun 11
🫘 Green Beans (Bush) Jun 4 – Jun 11
🌽 Sweet Corn Jun 4 – Jun 11
🌿 Basil Apr 16 – Apr 30 Jun 4 – Jun 11 Jun 11 – Jun 18
🧄 Garlic Fall: Aug 10 – Sep 7

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 Manassa's dates automatically after a lookup.

Reading the season in Manassa

At about 116 frost-free days, Manassa 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 Manassa, CO?

The average last spring frost in Manassa is around May 28, 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 Manassa, CO?

The average first fall frost in Manassa arrives around Sep 21. 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 Manassa?

About 116 frost-free days on average, from May 28 to Sep 21. 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 Manassa 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.