When is the last frost in San Mateo, CA?

For ZIP code 94403, the average last spring frost (32°F) is January 17, based on NOAA 1991-2020 climate normals for the Redwood City, CA weather station. There is a 1-in-10 chance of a frost after February 16.

When is the first frost in San Mateo, CA?

The average first fall frost (32°F) is December 12. There is a 1-in-10 chance of frost by November 24, so tender plants are at risk from that point on.

How long is the growing season in 94403?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 333 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 94403San Mateo, CA

The average last spring frost in San Mateo is January 17 and the average first fall frost is December 12, giving a typical growing season of about 333 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 17
Average first fall frost: Dec 12
Growing season: 333 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 25 · Feb 25 · Mar 31	Nov 8 · Nov 25 · Dec 14	272 days	100%
Frost / freeze (32°F)	Dec 20 · Jan 17 · Feb 16	Nov 24 · Dec 12 · Jan 14	333 days	88%
Hard freeze (28°F)	Dec 14 · Dec 31 · Jan 22	Dec 5 · Dec 26 · Jan 15	365 days	38%

Where these dates come from

ZIP code 94403 is matched to the NOAA station Redwood City, CA, 8.8 km away, at 31 ft elevation (5 ft higher than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Redwood City, CA (used)	31 ft	Jan 17	Dec 12
San Francisco Intl Ap, CA	8 ft	Dec 29	Dec 26
Woodside Fire Stn 1, CA	380 ft	Feb 25	Nov 25
Half Moon Bay, CA	27 ft	Feb 6	Dec 17

Frost dates near San Mateo

San Mateo, CA 94497 · last Feb 25, first Nov 25
Belmont, CA 94002 · last Jan 17, first Dec 12
Redwood City, CA 94065 · last Jan 17, first Dec 12
San Carlos, CA 94070 · last Jan 17, first Dec 12
Burlingame, CA 94010 · last Dec 29, first Dec 26
Millbrae, CA 94030 · last Dec 29, first Dec 26
San Francisco, CA 94128 · last Dec 29, first Dec 26
Atherton, CA 94027 · last Jan 17, first Dec 12

Frequently asked questions

When is the last frost in San Mateo, CA?: For ZIP code 94403, the average last spring frost (32°F) is January 17, based on NOAA 1991-2020 climate normals for the Redwood City, CA weather station. There is a 1-in-10 chance of a frost after February 16.
When is the first frost in San Mateo, CA?: The average first fall frost (32°F) is December 12. There is a 1-in-10 chance of frost by November 24, so tender plants are at risk from that point on.
How long is the growing season in 94403?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 333 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.