When is the last frost in Suisun City, CA?

For ZIP code 94585, the average last spring frost (32°F) is January 15, based on NOAA 1991-2020 climate normals for the Fairfield, CA weather station. There is a 1-in-10 chance of a frost after February 16.

When is the first frost in Suisun City, CA?

The average first fall frost (32°F) is December 14. There is a 1-in-10 chance of frost by November 29, so tender plants are at risk from that point on.

How long is the growing season in 94585?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 336 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 94585Suisun City, CA

The average last spring frost in Suisun City is January 15 and the average first fall frost is December 14, giving a typical growing season of about 336 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 15
Average first fall frost: Dec 14
Growing season: 336 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 23 · Feb 25 · Apr 4	Nov 13 · Dec 1 · Dec 21	278 days	100%
Frost / freeze (32°F)	Dec 22 · Jan 15 · Feb 16	Nov 29 · Dec 14 · Jan 9	336 days	88%
Hard freeze (28°F)	Dec 13 · Dec 31 · Jan 19	Dec 6 · Dec 24 · Jan 11	365 days	44%

Where these dates come from

ZIP code 94585 is matched to the NOAA station Fairfield, CA, 4.3 km away, at 40 ft elevation (30 ft higher than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Fairfield, CA (used)	40 ft	Jan 15	Dec 14
Vacaville Nut Tree Ap, CA	109 ft	Feb 18	Nov 28
Vacaville, CA	110 ft	Jan 31	Dec 11
Napa State Hospital, CA	35 ft	Feb 12	Dec 4

Frost dates near Suisun City

Fairfield, CA 94533 · last Jan 15, first Dec 14
Travis Afb, CA 94535 · last Jan 15, first Dec 14
Vacaville, CA 95687 · last Feb 18, first Nov 28
Elmira, CA 95625 · last Feb 18, first Nov 28
Birds Landing, CA 94512 · last Jan 12, first Dec 19
American Canyon, CA 94503 · last Mar 5, first Nov 21
Vallejo, CA 94591 · last Feb 28, first Nov 22
Benicia, CA 94510 · last Feb 28, first Nov 22

Frequently asked questions

When is the last frost in Suisun City, CA?: For ZIP code 94585, the average last spring frost (32°F) is January 15, based on NOAA 1991-2020 climate normals for the Fairfield, CA weather station. There is a 1-in-10 chance of a frost after February 16.
When is the first frost in Suisun City, CA?: The average first fall frost (32°F) is December 14. There is a 1-in-10 chance of frost by November 29, so tender plants are at risk from that point on.
How long is the growing season in 94585?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 336 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.