When to plant in Clayton, CA
USDA Zone 9bEverything below — frost dates, hardiness zone, and what to plant when in Clayton, California — is derived from the closest NOAA station with complete climate normals.
A generous ~289-day season lets Clayton gardeners direct-sow more and still ripen long-maturity crops like melons and winter squash. In zone 9b, frost is a minor factor for Clayton — most perennials thrive, and annual vegetables can go out early and stay late.
Frost probability
MT DIABLO JUNCTION · 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 Clayton’s own odds, recorded at MT DIABLO JUNCTION.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 20 | Apr 19 | Mar 16 | Nov 6 | Nov 29 | Dec 20 |
| 32°F | Apr 15 | Mar 8 | Jan 12 | Nov 23 | Dec 22 | Feb 11 |
| 28°F | Mar 23 | Feb 8 | Dec 21 | Dec 8 | Jan 16 | Mar 3 |
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 Clayton, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 13 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.
Clayton planting FAQ
When is the last spring frost in Clayton, CA?
Plan for the last spring frost in Clayton around March 8 (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 Clayton, CA?
In Clayton, the first 32°F freeze of fall lands around December 22 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Clayton in?
Clayton is in USDA hardiness zone 9b. In zone 9b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Clayton?
Clayton has about 289 frost-free days — a long growing season — between the average last spring frost (March 8) and first fall frost (December 22).
When should I plant tomatoes in Clayton?
For Clayton, sow tomatoes indoors about January 11–January 25 and move the seedlings out around March 15, after the last spring frost.
Never miss a window in Clayton
An email when it’s time to start seeds, transplant, and sow — timed to Clayton’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Concord · 7 km
- Pittsburg · 9 km
- Walnut Creek · 11 km
- Bay Point · 11 km
- Alamo · 12 km
- Antioch · 12 km
- Pleasant Hill · 13 km
- Blackhawk · 15 km
Frost dates recorded at MT DIABLO JUNCTION, 7 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 Clayton, CA — Frost Dates & Zone 9b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00045915. Retrieved from https://blissgarden.com/california/clayton.