Frost Dates for Thermal, CA 92274

Last spring frost January 31 · First fall frost December 2 · 305 frost-free days · USDA Zone 10a

Frost probability for 92274

Frost10%50%90%
Spring (last frost)March 8January 31January 8
Fall (first frost)November 8December 2December 25

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (11.7 km away); the 50% date is the median year.

Month by month in Thermal

MonthWhat to do
JanuaryLast frost around January 31. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
FebruaryFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
MarchSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
AprilHarvest regularly to encourage production. Monitor for pests and disease.
MayMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
JuneDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
JulyDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
AugustDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
SeptemberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
OctoberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
NovemberFirst fall frost approaching (around December 2). Transplant fall brassicas. Sow spinach, arugula, and radishes.
DecemberFirst frost around December 2. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.

What grows in a 305-day season

Frequently Asked Questions

What is the last frost date for Thermal, CA (ZIP 92274)?

The median last spring frost date for Thermal, CA (ZIP code 92274) is around January 31. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Thermal, CA?

The median first fall frost date for Thermal, CA is around December 2. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Thermal, CA?

The frost-free growing season in Thermal is about 305 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Thermal, CA?

Based on frost date patterns, Thermal falls approximately in 10a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Thermal, CA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around January 31). For Thermal, that's roughly December 6 to December 20. Transplant outdoors 1–2 weeks after your last frost.

Nearby and related