When is the last frost in Castro Valley, CA?

Frost occurs in about 45% of years at the nearest NOAA station (Hayward Air Terminal, CA), so there is no reliable average last frost date.

When is the first frost in Castro Valley, CA?

Frost occurs in about 45% of years at the nearest NOAA station.

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 94546Castro Valley, CA

Frost occurs in about 45% of years near Castro Valley, based on NOAA 1991-2020 records for the Hayward Air Terminal, CA station.

Frost occurs in about 45% of years. Frost-tender plants can usually grow year-round, but cover them if a rare cold snap is forecast.

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)	Dec 30 · Jan 29 · Feb 28	Nov 24 · Dec 12 · Jan 11	322 days	93%
Frost / freeze (32°F)	Dec 13 · Jan 2 · Jan 27	Dec 6 · Dec 25 · Jan 20	365 days	45%
Hard freeze (28°F)	—	—	365 days	5%

Where these dates come from

ZIP code 94546 is matched to the NOAA station Hayward Air Terminal, CA, 6.2 km away, at 43 ft elevation (160 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Hayward Air Terminal, CA (used)	43 ft	Jan 2	Dec 25
Oakland Metro Intl Ap, CA	6 ft	Jan 7	Dec 23
Fremont, CA	38 ft	Jan 7	Dec 22
Oakland Museum, CA	30 ft	—	—

Frost dates near Castro Valley

Hayward, CA 94541 · last Jan 2, first Dec 25
Castro Valley, CA 94552 · last Feb 15, first Dec 2
San Leandro, CA 94578 · last Jan 2, first Dec 25
San Lorenzo, CA 94580 · last Jan 2, first Dec 25
Oakland, CA 94603 · last Jan 7, first Dec 23
San Ramon, CA 94583 · last Feb 15, first Dec 2
Union City, CA 94587 · last Jan 7, first Dec 22
Moraga, CA 94570 · last Feb 27, first Dec 1

Frequently asked questions

When is the last frost in Castro Valley, CA?: Frost occurs in about 45% of years at the nearest NOAA station (Hayward Air Terminal, CA), so there is no reliable average last frost date.
When is the first frost in Castro Valley, CA?: Frost occurs in about 45% of years at the nearest NOAA station.
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.