Mt Hamilton, CA Frost Dates & Growing Season

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

Last spring frost
May 3
~50% chance of frost after
First fall frost
Nov 18
~50% chance of frost before
Growing season
199 days
frost-free stretch
USDA zone
≈ 9b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 7 May 3 Jun 5
First fall frost Dec 12 Nov 18 Oct 22
Hard freeze (28°F), median last Apr 10 · first Dec 7

Computed from NOAA 1991–2020 climate normals at the MT HAMILTON 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 Mt Hamilton

Computed from Mt Hamilton's own frost dates. Click any crop for the full zone-9 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Mar 8 – Mar 22 May 10 – May 17
🫑 Peppers Feb 22 – Mar 8 May 17 – May 24
🥬 Lettuce Mar 22 – Apr 5 Apr 5 – Apr 19 Apr 5 – May 3
🫛 Peas Mar 22 – Apr 5
🥕 Carrots Apr 12 – May 3
🥦 Broccoli Mar 15 – Mar 29 Apr 12 – Apr 26
🥬 Kale Mar 22 – Apr 5 Apr 5 – Apr 19 Apr 5 – Apr 19
🥒 Cucumbers Apr 5 – Apr 12 May 10 – May 17 May 10 – May 17
🥒 Zucchini Apr 5 – Apr 12 May 10 – May 17 May 10 – May 17
🫘 Green Beans (Bush) May 10 – May 17
🌽 Sweet Corn May 10 – May 17
🌿 Basil Mar 22 – Apr 5 May 10 – May 17 May 17 – May 24
🧄 Garlic Fall: Oct 7 – Nov 4

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 Mt Hamilton's dates automatically after a lookup.

Reading the season in Mt Hamilton

Roughly 199 frost-free days gives Mt Hamilton gardeners room for nearly every common vegetable. Warm-season crops go out after May 3; a fall garden sown in late summer matures comfortably before the Nov 18 frost.

Frequently asked questions

When is the last frost in Mt Hamilton, CA?

The average last spring frost in Mt Hamilton is around May 3, 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 Mt Hamilton, CA?

The average first fall frost in Mt Hamilton arrives around Nov 18. 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 Mt Hamilton?

About 199 frost-free days on average, from May 3 to Nov 18. That fits nearly all common vegetables, though the longest-season melons and sweet potatoes benefit from transplants.

What USDA zone is Mt Hamilton in?

USDA zone 9b 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.