When is the last frost in La Mesa, CA?

For ZIP code 91942, the average last spring frost (32°F) is January 6, based on NOAA 1991-2020 climate normals for the El Cajon, CA weather station. There is a 1-in-10 chance of a frost after February 7.

When is the first frost in La Mesa, CA?

The average first fall frost (32°F) is December 21. There is a 1-in-10 chance of frost by December 1, so tender plants are at risk from that point on.

How long is the growing season in 91942?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 350 days long.

Are these frost dates a forecast?

No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.

Frost dates for 91942La Mesa, CA

The average last spring frost in La Mesa is January 6 and the average first fall frost is December 21, giving a typical growing season of about 350 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 6
Average first fall frost: Dec 21
Growing season: 350 days

Frost risk by date

NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
Temperature	Last spring: 90% / 50% / 10% chance	First fall: 10% / 50% / 90% chance	Growing season (50%)	Years with at least one
Light frost (36°F)	Jan 6 · Feb 6 · Mar 3	Nov 18 · Dec 6 · Dec 29	300 days	99%
Frost / freeze (32°F)	Dec 13 · Jan 6 · Feb 7	Dec 1 · Dec 21 · Jan 15	350 days	73%
Hard freeze (28°F)	Dec 8 · Dec 31 · Jan 15	Dec 7 · Dec 30 · Jan 14	365 days	16%

Where these dates come from

ZIP code 91942 is matched to the NOAA station El Cajon, CA, 8.7 km away, at 495 ft elevation (86 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
El Cajon, CA (used)	495 ft	Jan 6	Dec 21
San Diego Montgomery Fld, CA	417 ft	—	—
San Diego Miramar Nas, CA	477 ft	—	—
San Diego Lindbergh Fld, CA	15 ft	—	—

Frost dates near La Mesa

La Mesa, CA 91943 · last Jan 6, first Dec 21
San Diego, CA 92119 · last Jan 6, first Dec 21
Spring Valley, CA 91976 · last Jan 6, first Dec 21
Lemon Grove, CA 91946 · last Jan 6, first Dec 21
El Cajon, CA 92020 · last Jan 6, first Dec 21
Santee, CA 92072 · last Jan 6, first Dec 21
Lakeside, CA 92040 · last Jan 6, first Dec 21
Bonita, CA 91902 · last —, first —

Frequently asked questions

When is the last frost in La Mesa, CA?: For ZIP code 91942, the average last spring frost (32°F) is January 6, based on NOAA 1991-2020 climate normals for the El Cajon, CA weather station. There is a 1-in-10 chance of a frost after February 7.
When is the first frost in La Mesa, CA?: The average first fall frost (32°F) is December 21. There is a 1-in-10 chance of frost by December 1, so tender plants are at risk from that point on.
How long is the growing season in 91942?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 350 days long.
Are these frost dates a forecast?: No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.