Copco #1 Dam, CA Frost Dates & Growing Season

The two dates every Copco #1 Dam garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 4
~50% chance of frost after
First fall frost
Oct 21
~50% chance of frost before
Growing season
170 days
frost-free stretch
USDA zone
≈ 8b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 15 May 4 May 31
First fall frost Nov 4 Oct 21 Oct 10
Hard freeze (28°F), median last Apr 16 · first Nov 4

Computed from NOAA 1991–2020 climate normals at the COPCO #1 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 Copco #1 Dam

Computed from Copco #1 Dam's own frost dates. Click any crop for the full zone-8 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Mar 9 – Mar 23 May 11 – May 18
🫑 Peppers Feb 23 – Mar 9 May 18 – May 25
🥬 Lettuce Mar 23 – Apr 6 Apr 6 – Apr 20 Apr 6 – May 4
🫛 Peas Mar 23 – Apr 6
🥕 Carrots Apr 13 – May 4
🥦 Broccoli Mar 16 – Mar 30 Apr 13 – Apr 27
🥬 Kale Mar 23 – Apr 6 Apr 6 – Apr 20 Apr 6 – Apr 20
🥒 Cucumbers Apr 6 – Apr 13 May 11 – May 18 May 11 – May 18
🥒 Zucchini Apr 6 – Apr 13 May 11 – May 18 May 11 – May 18
🫘 Green Beans (Bush) May 11 – May 18
🌽 Sweet Corn May 11 – May 18
🌿 Basil Mar 23 – Apr 6 May 11 – May 18 May 18 – May 25
🧄 Garlic Fall: Sep 9 – Oct 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 Copco #1 Dam's dates automatically after a lookup.

Reading the season in Copco #1 Dam

Roughly 170 frost-free days gives Copco #1 Dam gardeners room for nearly every common vegetable. Warm-season crops go out after May 4; a fall garden sown in late summer matures comfortably before the Oct 21 frost.

Frequently asked questions

When is the last frost in Copco #1 Dam, CA?

The average last spring frost in Copco #1 Dam is around May 4, 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 Copco #1 Dam, CA?

The average first fall frost in Copco #1 Dam arrives around Oct 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 Copco #1 Dam?

About 170 frost-free days on average, from May 4 to Oct 21. That fits nearly all common vegetables, though the longest-season melons and sweet potatoes benefit from transplants.

What USDA zone is Copco #1 Dam in?

USDA zone 8b 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.