When to plant in Suisun City, CA
USDA Zone 9bEverything below — frost dates, hardiness zone, and what to plant when in Suisun City, California — is derived from the closest NOAA station with complete climate normals.
Suisun City enjoys a long ~333-day frost-free season — you can succession-sow, fit in a second crop, and grow long-season heat-lovers with room to spare. Zone 9b is warm enough that Suisun City can grow subtropical perennials, and the short (or absent) frost period barely limits the annual calendar.
The average last spring frost in Suisun City is now 13 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
FAIRFIELD · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Suisun City’s own odds, recorded at FAIRFIELD.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Apr 4 | Feb 25 | Jan 23 | Nov 13 | Dec 1 | Dec 21 |
| 32°F | Feb 16 | Jan 15 | Dec 22 | Nov 29 | Dec 14 | Jan 9 |
| 28°F | Jan 19 | Dec 31 | Dec 13 | Dec 6 | Dec 24 | Jan 11 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Nothing new to sow or transplant outdoors in the next few weeks — a seasonal lull. Check the full-year calendar below for the next window.
Full-year planting calendar
Each bar is the exact window to take a planting action in Suisun City, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 17 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Suisun City planting FAQ
When is the last spring frost in Suisun City, CA?
Plan for the last spring frost in Suisun City around January 15 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Suisun City, CA?
In Suisun City, the first 32°F freeze of fall lands around December 14 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Suisun City in?
Suisun City is in USDA hardiness zone 9b. In zone 9b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Suisun City?
There are roughly 333 frost-free days in Suisun City (a long growing season), running from the average last frost around January 15 to the first fall frost near December 14.
When should I plant tomatoes in Suisun City?
In Suisun City, start tomato seeds indoors around November 20–December 4, then transplant seedlings outdoors around January 22 once the danger of frost has passed.
Never miss a window in Suisun City
An email when it’s time to start seeds, transplant, and sow — timed to Suisun City’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at FAIRFIELD, 6 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Suisun City, CA — Frost Dates & Zone 9b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00042934. Retrieved from https://blissgarden.com/california/suisun-city.