Blanca 4 NW, CO Frost Dates & Growing Season

The two dates every Blanca 4 NW garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 25
~50% chance of frost after
First fall frost
Sep 22
~50% chance of frost before
Growing season
120 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 11 May 25 Jun 12
First fall frost Oct 3 Sep 22 Sep 10
Hard freeze (28°F), median last May 13 · first Oct 1

Computed from NOAA 1991–2020 climate normals at the BLANCA 4 NW 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 Blanca 4 NW

Computed from Blanca 4 NW'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 30 – Apr 13 Jun 1 – Jun 8
🫑 Peppers Mar 16 – Mar 30 Jun 8 – Jun 15
🥬 Lettuce Apr 13 – Apr 27 Apr 27 – May 11 Apr 27 – May 25
🫛 Peas Apr 13 – Apr 27
🥕 Carrots May 4 – May 25
🥦 Broccoli Apr 6 – Apr 20 May 4 – May 18
🥬 Kale Apr 13 – Apr 27 Apr 27 – May 11 Apr 27 – May 11
🥒 Cucumbers Apr 27 – May 4 Jun 1 – Jun 8 Jun 1 – Jun 8
🥒 Zucchini Apr 27 – May 4 Jun 1 – Jun 8 Jun 1 – Jun 8
🫘 Green Beans (Bush) Jun 1 – Jun 8
🌽 Sweet Corn Jun 1 – Jun 8
🌿 Basil Apr 13 – Apr 27 Jun 1 – Jun 8 Jun 8 – Jun 15
🧄 Garlic Fall: Aug 11 – Sep 8

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 Blanca 4 NW's dates automatically after a lookup.

Reading the season in Blanca 4 NW

At about 120 frost-free days, Blanca 4 NW 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 Blanca 4 NW, CO?

The average last spring frost in Blanca 4 NW is around May 25, 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 Blanca 4 NW, CO?

The average first fall frost in Blanca 4 NW arrives around Sep 22. 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 Blanca 4 NW?

About 120 frost-free days on average, from May 25 to Sep 22. 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 Blanca 4 NW 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.