When to plant in Windsor, CA
USDA Zone 9aEverything below — frost dates, hardiness zone, and what to plant when in Windsor, California — is derived from the closest NOAA station with complete climate normals.
A generous ~263-day season lets Windsor gardeners direct-sow more and still ripen long-maturity crops like melons and winter squash. In zone 9a, frost is a minor factor for Windsor — most perennials thrive, and annual vegetables can go out early and stay late.
Frost probability
SANTA ROSA SONOMA CO AP · 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 Windsor’s own odds, recorded at SANTA ROSA SONOMA CO AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 1 | Apr 12 | Mar 17 | Oct 16 | Nov 3 | Nov 21 |
| 32°F | Apr 2 | Mar 2 | Jan 27 | Nov 1 | Nov 20 | Dec 10 |
| 28°F | Feb 23 | Jan 23 | Dec 20 | Nov 15 | Dec 5 | Jan 7 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Windsor, 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.
Windsor planting FAQ
When is the last spring frost in Windsor, CA?
Plan for the last spring frost in Windsor around March 2 (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 Windsor, CA?
The first fall frost in Windsor typically arrives around November 20 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Windsor in?
Windsor is in USDA hardiness zone 9a. In zone 9a, winters are mild — many tender perennials overwinter here.
How long is the growing season in Windsor?
Windsor has about 263 frost-free days — a long growing season — between the average last spring frost (March 2) and first fall frost (November 20).
When should I plant tomatoes in Windsor?
For Windsor, sow tomatoes indoors about January 5–January 19 and move the seedlings out around March 9, after the last spring frost.
Never miss a window in Windsor
An email when it’s time to start seeds, transplant, and sow — timed to Windsor’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Healdsburg · 10 km
- Santa Rosa · 14 km
- Rohnert Park · 24 km
- Petaluma · 37 km
- Sonoma · 41 km
- Clearlake · 49 km
- Napa · 52 km
- Novato · 56 km
Frost dates recorded at SANTA ROSA SONOMA CO AP, 4 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 Windsor, CA — Frost Dates & Zone 9a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00023213. Retrieved from https://blissgarden.com/california/windsor.