Frost Dates for Porterville, CA 93257

Last spring frost March 5 · First fall frost November 17 · 257 frost-free days · USDA Zone 9b

Frost probability for 93257

Frost10%50%90%
Spring (last frost)April 12March 5April 29
Fall (first frost)November 1November 17December 3

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (28.0 km away); the 50% date is the median year.

Frost dates by ZIP code in Porterville, CA

ZIPLast spring frost (50%)First fall frost (50%)Zone
93257March 5November 179b
93258February 8November 289b

Month by month in Porterville

MonthWhat to do
JanuaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around March 5). Start tomatoes about two weeks later, 6–8 weeks before last frost.
FebruaryStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
MarchLast frost around March 5. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
AprilFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
MaySuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JuneHarvest regularly to encourage production. Monitor for pests and disease.
JulyMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
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.
OctoberFirst fall frost approaching (around November 17). Transplant fall brassicas. Sow spinach, arugula, and radishes.
NovemberFirst frost around November 17. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
DecemberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.

What grows in a 257-day season

Frequently Asked Questions

What is the last frost date for Porterville, CA (ZIP 93257)?

The median last spring frost date for Porterville, CA (ZIP code 93257) is around March 5. 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 Porterville, CA?

The median first fall frost date for Porterville, CA is around November 17. 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 Porterville, CA?

The frost-free growing season in Porterville is about 257 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 Porterville, CA?

Based on frost date patterns, Porterville falls approximately in 9b. 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 Porterville, CA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around March 5). For Porterville, that's roughly January 9 to January 23. Transplant outdoors 1–2 weeks after your last frost.

Nearby and related