Chiriaco Summit, CA Frost Dates & Growing Season

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

Last spring frost
Feb 5
~50% chance of frost after
First fall frost
Dec 17
~50% chance of frost before
Growing season
315 days
frost-free stretch
USDA zone
≈ 10b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Dec 30 Feb 5 Mar 5
First fall frost Jan 10 Dec 17 Nov 25
Hard freeze (28°F), median last Jan 10 · first Dec 31

Computed from NOAA 1991–2020 climate normals at the CHIRIACO SUMMIT 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 Chiriaco Summit

Computed from Chiriaco Summit's own frost dates. Click any crop for the full zone-10 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Dec 11 – Dec 25 Feb 12 – Feb 19
🫑 Peppers Nov 27 – Dec 11 Feb 19 – Feb 26
🥬 Lettuce Dec 25 – Jan 8 Jan 8 – Jan 22 Jan 8 – Feb 5
🫛 Peas Dec 25 – Jan 8
🥕 Carrots Jan 15 – Feb 5
🥦 Broccoli Dec 18 – Jan 1 Jan 15 – Jan 29
🥬 Kale Dec 25 – Jan 8 Jan 8 – Jan 22 Jan 8 – Jan 22
🥒 Cucumbers Jan 8 – Jan 15 Feb 12 – Feb 19 Feb 12 – Feb 19
🥒 Zucchini Jan 8 – Jan 15 Feb 12 – Feb 19 Feb 12 – Feb 19
🫘 Green Beans (Bush) Feb 12 – Feb 19
🌽 Sweet Corn Feb 12 – Feb 19
🌿 Basil Dec 25 – Jan 8 Feb 12 – Feb 19 Feb 19 – Feb 26
🧄 Garlic Fall: Nov 5 – Dec 3

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 Chiriaco Summit's dates automatically after a lookup.

Reading the season in Chiriaco Summit

With roughly 315 frost-free days, Chiriaco Summit gardens fit long-season crops — melons, winter squash, sweet potatoes — with room left for spring and fall rounds of greens and roots. The first frost around Dec 17 is late enough that fall planting is a full second season, not an afterthought.

Frequently asked questions

When is the last frost in Chiriaco Summit, CA?

The average last spring frost in Chiriaco Summit is around Feb 5, 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 Chiriaco Summit, CA?

The average first fall frost in Chiriaco Summit arrives around Dec 17. 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 Chiriaco Summit?

About 315 frost-free days on average, from Feb 5 to Dec 17. That comfortably fits long-season crops like melons and winter squash, plus spring and fall plantings of cool-season vegetables.

What USDA zone is Chiriaco Summit in?

USDA zone 10b 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.