Frost dates / California / Pomona

Frost dates in Pomona, CA

The station on this page is POMONA/FAIRPLEX, CA US (USC00047050), 1.6 miles from the city point. Population in the Census 2024 estimate is 147,966.

Zone 10aUSDA average annual extreme minimum 30°F to 35°F, from ZIP 91766 (1.2 miles from the city point used on this page).

Median last 32°F is January 8. Median first 32°F is December 28. The 50% growing-season length is 354 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 14	Earlier date. A last 32°F on or after this day is common.
50%	January 8	Median.
10%	February 18	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 5	Earlier date. A first 32°F on or before this day is uncommon.
50%	December 28	Median.
90%	February 2	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%	354
90%	315

36°F threshold

	10%	50%	90%
Last, on or after	March 9	February 8	December 29
First, on or before	November 21	December 10	December 26
Season at least	342 days	303 days	264 days

Station POMONA/FAIRPLEX, CA US (USC00047050). Completeness flag R, 16 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 65.1%. Freeze dates are conditional on that threshold occurring. Elevation 304.5 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 Pomona · Zone 10a

Check a crop against this station

Pomona, 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: POMONA/FAIRPLEX, CA US (USC00047050), 1.6 miles. Median last 32°F January 8. Median first 32°F December 28. The 50% growing-season length is 354 days.

Open the ZIP page · Crop guides for California

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	February 18	January 8	December 14
First 32°F on or before	December 5	December 28	February 2

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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