Frost dates / California / South San Francisco

Frost dates in South San Francisco, CA

The station on this page is SAN FRANCISCO INTL AP, CA US (USW00023234), 2.5 miles from the city point. Population in the Census 2024 estimate is 64,660.

Zone 10aUSDA average annual extreme minimum 30°F to 35°F, from ZIP 94080 (2.3 miles from the city point used on this page).

Median last 32°F is December 29. Median first 32°F is December 26. The 50% growing-season length is 365 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	December 11	Earlier date. A last 32°F on or after this day is common.
50%	December 29	Median.
10%	January 13	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	December 11	Earlier date. A first 32°F on or before this day is uncommon.
50%	December 26	Median.
90%	January 13	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	365
50%	365
90%	362

36°F threshold

	10%	50%	90%
Last, on or after	February 14	January 8	December 16
First, on or before	December 5	December 24	January 24
Season at least	365 days	353 days	319 days

Station SAN FRANCISCO INTL AP, CA US (USW00023234). Completeness flag S, 26 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 11.6%. Freeze dates are conditional on that threshold occurring. Elevation 2.4 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Planting calendar for South San Francisco · Zone 10a

Check a crop against this station

South San Francisco, CA

Zone 10aAverage annual extreme minimum 30°F to 35°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

California. Nearest qualified station: SAN FRANCISCO INTL AP, CA US (USW00023234), 2.5 miles. Median last 32°F December 29. Median first 32°F December 26. The 50% growing-season length is 365 days.

Open the ZIP page · Crop guides for California

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	January 13	December 29	December 11
First 32°F on or before	December 11	December 26	January 13

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

A wall calendar surrounded by vegetables, herbs, seed packets, and watering cans.

Planting calendar

Windows below are from UC ANR, UC Master Gardener Program, Time of planting, retrieved 2026-10-10. North and North Coast = Monterey County north; South Coast = San Luis Obispo County south; Interior Valleys = Sacramento, San Joaquin, and similar valleys; Desert Valleys = Imperial and Coachella Valleys. Source line on the page: California Master Gardener Handbook, Table 13.2, Adapted from Vegetable Gardening Illustrated 1994.

Crop

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