When is the last frost in Riverside, CA?

For ZIP code 92505, the average last spring frost (32°F) is January 9, based on NOAA 1991-2020 climate normals for the Riverside Muni Ap, CA weather station. There is a 1-in-10 chance of a frost after February 21.

When is the first frost in Riverside, CA?

The average first fall frost (32°F) is December 30. There is a 1-in-10 chance of frost by December 5, so tender plants are at risk from that point on.

How long is the growing season in 92505?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 362 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 92505Riverside, CA

The average last spring frost in Riverside is January 9 and the average first fall frost is December 30, giving a typical growing season of about 362 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 9
Average first fall frost: Dec 30
Growing season: 362 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 2 · Feb 13 · Mar 13	Nov 23 · Dec 12 · Jan 9	305 days	98%
Frost / freeze (32°F)	Dec 16 · Jan 9 · Feb 21	Dec 5 · Dec 30 · Feb 6	362 days	58%
Hard freeze (28°F)	—	—	365 days	7%

Where these dates come from

ZIP code 92505 is matched to the NOAA station Riverside Muni Ap, CA, 5.5 km away, at 805 ft elevation (83 ft higher than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Riverside Muni Ap, CA (used)	805 ft	Jan 9	Dec 30
Riverside Fire Stn 3, CA	840 ft	Jan 9	Dec 25
Riverside Citrus Exp, CA	986 ft	Jan 10	Jan 2
Chino Ap, CA	650 ft	Jan 17	Dec 19

Frost dates near Riverside

Riverside, CA 92503 · last Jan 9, first Dec 30
Norco, CA 92860 · last Jan 17, first Dec 19
Corona, CA 92879 · last Jan 17, first Dec 19
Mira Loma, CA 91752 · last Jan 9, first Dec 30
March Air Reserve Base, CA 92518 · last Jan 9, first Dec 25
Fontana, CA 92337 · last Jan 10, first Jan 2
Chino, CA 91708 · last Jan 17, first Dec 19
Ontario, CA 91761 · last Jan 17, first Dec 19

Frequently asked questions

When is the last frost in Riverside, CA?: For ZIP code 92505, the average last spring frost (32°F) is January 9, based on NOAA 1991-2020 climate normals for the Riverside Muni Ap, CA weather station. There is a 1-in-10 chance of a frost after February 21.
When is the first frost in Riverside, CA?: The average first fall frost (32°F) is December 30. There is a 1-in-10 chance of frost by December 5, so tender plants are at risk from that point on.
How long is the growing season in 92505?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 362 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.