Frost Dates for Porterville, CA 93258

Porterville has 2 ZIP codes. The Porterville, CA frost page lists all of them with their dates.

Last spring frost February 8 · First fall frost November 28 · 293 frost-free days · USDA Zone 9b

Frost probability for 93258

Frost10%50%90%
Spring (last frost)March 20February 8December 22
Fall (first frost)November 11November 28December 15

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (11.9 km away); the 50% date is the median year.

Month by month in Porterville

MonthWhat to do
JanuaryStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
FebruaryLast frost around February 8. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
MarchFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
AprilSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
MayHarvest regularly to encourage production. Monitor for pests and disease.
JuneMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
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.
OctoberFirst fall frost approaching (around November 28). Transplant fall brassicas. Sow spinach, arugula, and radishes.
NovemberFirst frost around November 28. 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 293-day season

Frequently Asked Questions

What is the last frost date for Porterville, CA (ZIP 93258)?

The median last spring frost date for Porterville, CA (ZIP code 93258) is around February 8. 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 28. 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 293 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 February 8). For Porterville, that's roughly December 14 to December 28. Transplant outdoors 1–2 weeks after your last frost.

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