When is the last frost in Walnut Creek, CA?

For ZIP code 94598, the average last spring frost (32°F) is January 7, based on NOAA 1991-2020 climate normals for the Concord Wwtp, CA weather station. There is a 1-in-10 chance of a frost after February 1.

When is the first frost in Walnut Creek, CA?

The average first fall frost (32°F) is December 19. 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 94598?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 346 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 94598Walnut Creek, CA

The average last spring frost in Walnut Creek is January 7 and the average first fall frost is December 19, giving a typical growing season of about 346 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 7
Average first fall frost: Dec 19
Growing season: 346 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 9 · Mar 6	Nov 15 · Dec 2 · Dec 24	297 days	99%
Frost / freeze (32°F)	Dec 19 · Jan 7 · Feb 1	Dec 1 · Dec 19 · Jan 12	346 days	80%
Hard freeze (28°F)	Dec 14 · Dec 31 · Jan 20	Dec 10 · Dec 29 · Jan 14	365 days	25%

Where these dates come from

ZIP code 94598 is matched to the NOAA station Concord Wwtp, CA, 8.1 km away, at 40 ft elevation (101 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Concord Wwtp, CA (used)	40 ft	Jan 7	Dec 19
Concord Buchanan Fld, CA	18 ft	Jan 9	Dec 14
Mt Diablo Junction, CA	2,170 ft	Mar 8	Dec 22
Martinez Wtp, CA	40 ft	Feb 28	Nov 22

Frost dates near Walnut Creek

Walnut Creek, CA 94596 · last Jan 7, first Dec 19
Concord, CA 94518 · last Jan 7, first Dec 19
Pleasant Hill, CA 94523 · last Jan 7, first Dec 19
Alamo, CA 94507 · last Jan 3, first Jan 1
Lafayette, CA 94549 · last Jan 3, first Jan 1
Clayton, CA 94517 · last Feb 15, first Dec 2
Diablo, CA 94528 · last Feb 27, first Dec 1
Moraga, CA 94556 · last Jan 3, first Jan 1

Frequently asked questions

When is the last frost in Walnut Creek, CA?: For ZIP code 94598, the average last spring frost (32°F) is January 7, based on NOAA 1991-2020 climate normals for the Concord Wwtp, CA weather station. There is a 1-in-10 chance of a frost after February 1.
When is the first frost in Walnut Creek, CA?: The average first fall frost (32°F) is December 19. 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 94598?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 346 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.