Frost Dates
Frost Dates · California

Frost dates for El Cajon, California

California · first & last freeze, from NOAA 1991–2020 climate normals

Typical last spring freeze (32°F)
January 6
median date, 1991–2020
Typical first fall freeze (32°F)
December 21
median date, 1991–2020
Typical frost-free season
349 days
between the median dates

In a typical year, the last spring freeze around El Cajon comes near January 6 and the first fall freeze near December 21. One year in ten, a freeze still arrives after February 7 in spring — and one year in ten, the first fall freeze has already landed by December 1. NCEI's own growing-season statistic (days between freezes, percentiled per year) puts the median at 350 days.

JFMAMJJASONDJanuary 6December 21
The year at a glance: blue bands span the 9-in-10 to 1-in-10 range where the last spring / first fall 32°F freeze lands; the green band is the typical frost-free window between the median dates. Measured at El Cajon, CA (USC00042706), 1.9 mi from the city's census reference point, elev. 495 ft. NOAA/NCEI 1991–2020 normals.

Freeze-date probabilities, three thresholds

ThresholdLast spring — 9 in 10 years past byLast spring — typical (median)Last spring — 1 in 10 years later thanFirst fall — 1 in 10 years byFirst fall — typical (median)First fall — 9 in 10 years by
36°F — near-freezing (frost can occur)January 6February 6March 3November 18December 6December 29
32°F — freezingDecember 13January 6February 7December 1December 21January 15
28°F — hard freezeDecember 8December 31January 15December 7December 30January 14

Measured at El Cajon, CA (USC00042706), 1.9 mi from the city's census reference point, elev. 495 ft. NOAA/NCEI 1991–2020 normals. Read each date column as odds over the 30-year record — e.g. "9 in 10 years past by" means only one spring in ten saw a later freeze than that date.

Frost-free windows (computed)

Window (32°F ends)OpensClosesLength
Cautious (1-in-10 freeze risk at each end)February 7December 1297 days
Typical (median freeze dates)January 6December 21349 days
Gambler's (9-in-10 freeze risk at each end)December 13January 15365 days (effectively year-round at this risk level)

Pure arithmetic on the freeze-date percentiles above — the "cautious" window opens on the date only 1 year in 10 still sees a later spring freeze, and closes on the date by which only 1 year in 10 has already frozen.

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