When is the last frost in Porterville, CA?

The average last spring frost (50% probability of 32°F) in Porterville is around January 20, based on NOAA/NCEI 1991–2020 normals at the Porterville, CA station (9.5 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Porterville?

The average first fall frost in Porterville, CA is around December 13, giving roughly a 330-day frost-free growing season.

What planting zone is Porterville, CA?

Porterville is in USDA plant hardiness zone 9b (average annual extreme minimum temperature 25 to 30°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Porterville?

In Porterville, CA the warmest month is July (avg high 98.4°F) and the coldest is December (avg low 38.8°F). It averages about 11″ of precipitation a year.

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Porterville, CA Planting Calendar & Frost Dates

USDA hardiness zone 9b · ZIP 93257 · elevation 120′ · NOAA & USDA data

Porterville is in USDA hardiness zone 9b (winters can dip to 25 to 30°F), with a growing season of about 330 days between the average last spring frost (January 20) and first fall frost (December 13). The warmest month is July (avg high 98.4°F); the coldest is December (avg low 38.8°F). It averages 11″ of precipitation a year. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp 25 to 30°F

Last spring frost

January 20

avg (50% prob, 32°F)

First fall frost

December 13

avg (50% prob, 32°F)

Growing season

330 days

frost-free window

Warmest month

July

avg high 98.4°F

Month-by-month typical weather in Porterville

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Porterville, CA (9.5 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	59.1	39.7	49.4	2.1	–
February	64.6	43.1	53.9	1.9	–
March	70.5	46.6	58.5	2	–
April	76	49.7	62.9	1	–
May	84.1	56.3	70.2	0.3	–
June	92.7	62.5	77.6	0.1	–
July	98.4	68.4	83.4	0.1	–
August	97.1	66.7	81.9	0	–
September	92.3	62.3	77.3	0.1	–
October	82	53.4	67.7	0.6	–
November	68.4	44.3	56.3	1	–
December	59.2	38.8	49	1.9	–

What to plant when in Porterville

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: December 9 · Transplant out: January 27
Peppers	warm	Start seeds indoors: November 25 · Transplant out: February 3
Cucumbers	warm	Direct sow: January 27
Zucchini / squash	warm	Direct sow: January 27
Bush beans	warm	Direct sow: January 27
Sweet corn	warm	Direct sow: January 27
Basil	warm	Transplant out: January 27
Peas	cool	Sow (spring): December 16 · Sow (fall): October 18
Spinach	cool	Sow (spring): December 9 · Sow (fall): October 18
Lettuce	cool	Sow (spring): December 23 · Sow (fall): October 18
Kale	cool	Transplant (spring): December 30 · Sow (fall): October 4
Broccoli	cool	Transplant (spring): January 6
Carrots	cool	Sow (spring): December 30 · Sow (fall): October 4
Onions	cool	Transplant (spring): December 23
Potatoes	cool	Plant seed potatoes: January 6
Radishes	cool	Sow (spring): December 23 · Sow (fall): November 1

Dates are computed from Porterville's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

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Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Porterville, CA, 9.5 mi (confidence: high). Monthly weather normals: Porterville, CA, 9.5 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.