When is the last frost in Riverside, CA?

For ZIP code 92515, the average last spring frost (32°F) is January 9, based on NOAA 1991-2020 climate normals for the Riverside Fire Stn 3, CA weather station. There is a 1-in-10 chance of a frost after February 25.

When is the first frost in Riverside, CA?

The average first fall frost (32°F) is December 25. 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 92515?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 353 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 92515Riverside, CA

The average last spring frost in Riverside is January 9 and the average first fall frost is December 25, giving a typical growing season of about 353 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 9
Average first fall frost: Dec 25
Growing season: 353 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 8 · Feb 19 · Mar 22	Nov 15 · Dec 6 · Jan 1	293 days	99%
Frost / freeze (32°F)	Dec 16 · Jan 9 · Feb 25	Dec 1 · Dec 25 · Jan 27	353 days	69%
Hard freeze (28°F)	Dec 13 · Dec 31 · Jan 16	Nov 30 · Dec 29 · Jan 13	365 days	11%

Where these dates come from

ZIP code 92515 is matched to the NOAA station Riverside Fire Stn 3, CA, 0.8 km away, at 840 ft elevation (13 ft higher than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Riverside Fire Stn 3, CA (used)	840 ft	Jan 9	Dec 25
Riverside Citrus Exp, CA	986 ft	Jan 10	Jan 2
Riverside Muni Ap, CA	805 ft	Jan 9	Dec 30
Redlands, CA	1,410 ft	Jan 27	Dec 19

Frost dates near Riverside

Riverside, CA 92502 · last Jan 9, first Dec 25
March Air Reserve Base, CA 92518 · last Jan 9, first Dec 25
Grand Terrace, CA 92313 · last Jan 10, first Jan 2
Bloomington, CA 92316 · last Jan 10, first Jan 2
Mira Loma, CA 91752 · last Jan 9, first Dec 30
Fontana, CA 92337 · last Jan 10, first Jan 2
Colton, CA 92324 · last Jan 27, first Dec 19
Moreno Valley, CA 92557 · last Jan 27, first Dec 19

Frequently asked questions

When is the last frost in Riverside, CA?: For ZIP code 92515, the average last spring frost (32°F) is January 9, based on NOAA 1991-2020 climate normals for the Riverside Fire Stn 3, CA weather station. There is a 1-in-10 chance of a frost after February 25.
When is the first frost in Riverside, CA?: The average first fall frost (32°F) is December 25. 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 92515?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 353 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.