San Luis 1 S, CO Frost Dates & Growing Season

The two dates every San Luis 1 S garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 31
~50% chance of frost after
First fall frost
Sep 23
~50% chance of frost before
Growing season
115 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 14 May 31 Jun 14
First fall frost Oct 5 Sep 23 Sep 10
Hard freeze (28°F), median last May 13 · first Sep 30

Computed from NOAA 1991–2020 climate normals at the SAN LUIS 1 S 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 San Luis 1 S

Computed from San Luis 1 S'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 5 – Apr 19 Jun 7 – Jun 14
🫑 Peppers Mar 22 – Apr 5 Jun 14 – Jun 21
🥬 Lettuce Apr 19 – May 3 May 3 – May 17 May 3 – May 31
🫛 Peas Apr 19 – May 3
🥕 Carrots May 10 – May 31
🥦 Broccoli Apr 12 – Apr 26 May 10 – May 24
🥬 Kale Apr 19 – May 3 May 3 – May 17 May 3 – May 17
🥒 Cucumbers May 3 – May 10 Jun 7 – Jun 14 Jun 7 – Jun 14
🥒 Zucchini May 3 – May 10 Jun 7 – Jun 14 Jun 7 – Jun 14
🫘 Green Beans (Bush) Jun 7 – Jun 14
🌽 Sweet Corn Jun 7 – Jun 14
🌿 Basil Apr 19 – May 3 Jun 7 – Jun 14 Jun 14 – Jun 21
🧄 Garlic Fall: Aug 12 – Sep 9

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 San Luis 1 S's dates automatically after a lookup.

Reading the season in San Luis 1 S

At about 115 frost-free days, San Luis 1 S 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 San Luis 1 S, CO?

The average last spring frost in San Luis 1 S is around May 31, 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 San Luis 1 S, CO?

The average first fall frost in San Luis 1 S arrives around Sep 23. 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 San Luis 1 S?

About 115 frost-free days on average, from May 31 to Sep 23. 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 San Luis 1 S 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.