Frost dates / California / San Luis Obispo

Frost dates in San Luis Obispo, CA

The station on this page is SAN LUIS OBISPO AP, CA US (USW00093206), 2.5 miles from the city point. Population in the Census 2024 estimate is 49,729.

Zone 9bUSDA average annual extreme minimum 25°F to 30°F, from ZIP 93410 (2.7 miles from the city point used on this page).

Median last 32°F is January 31. Median first 32°F is December 11. The 50% growing-season length is 319 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 23	Earlier date. A last 32°F on or after this day is common.
50%	January 31	Median.
10%	March 7	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%	November 20	Earlier date. A first 32°F on or before this day is uncommon.
50%	December 11	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%	357
50%	319
90%	273

28°F threshold

	10%	50%	90%
Last, on or after	February 1	January 3	December 11
First, on or before	December 4	December 28	January 26
Season at least	365 days	365 days	335 days

36°F threshold

	10%	50%	90%
Last, on or after	April 16	March 17	February 6
First, on or before	November 3	November 24	December 11
Season at least	295 days	250 days	215 days

Station SAN LUIS OBISPO AP, CA US (USW00093206). Completeness flag R, 14 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 95%. Freeze dates are conditional on that threshold occurring. Elevation 61 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 San Luis Obispo · Zone 9b

Check a crop against this station

San Luis Obispo, CA

Zone 9bAverage annual extreme minimum 25°F to 30°F

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

California. Nearest qualified station: SAN LUIS OBISPO AP, CA US (USW00093206), 2.5 miles. Median last 32°F January 31. Median first 32°F December 11. The 50% growing-season length is 319 days.

Open the ZIP page · Crop guides for California

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	March 7	January 31	December 23
First 32°F on or before	November 20	December 11	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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