Windsor, CA planting zone & frost dates
Windsor is in USDA hardiness zone 9a. The last spring frost usually comes around March 2 and the first fall frost around November 20, for a growing season of about 262 days.
Planting calendar for Windsor
Dates are counted from the average last spring frost (March 2) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Jan 5 – Jan 19 Transplant outdoors: Mar 9 – Mar 16 |
| Peppers | Start seeds indoors: Dec 22 – Jan 5 Transplant outdoors: Mar 16 – Mar 23 |
| Eggplant | Start seeds indoors: Dec 22 – Jan 5 Transplant outdoors: Mar 16 – Mar 23 |
| Broccoli | Start seeds indoors: Dec 22 – Jan 5 Transplant outdoors: Feb 2 – Feb 16 |
| Cabbage | Start seeds indoors: Dec 22 – Jan 5 Transplant outdoors: Feb 2 – Feb 16 |
| Onions (sets) | Plant outdoors: Feb 2 – Feb 16 |
| Peas | Sow outdoors: Jan 19 – Feb 2 |
| Spinach | Sow outdoors: Jan 19 – Feb 2 |
| Lettuce | Sow outdoors: Feb 2 – Feb 16 |
| Carrots | Sow outdoors: Feb 2 – Feb 16 |
| Potatoes | Plant outdoors: Feb 2 – Feb 16 |
| Beans | Sow outdoors: Mar 9 – Mar 16 |
| Sweet corn | Sow outdoors: Mar 9 – Mar 16 |
| Cucumbers | Sow outdoors: Mar 9 – Mar 16 |
| Squash & zucchini | Sow outdoors: Mar 9 – Mar 16 |
| Basil | Start seeds indoors: Jan 19 – Feb 2 Transplant outdoors: Mar 9 – Mar 16 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 25 (8 weeks before the average first fall frost on Nov 20).
Useful for zone 9a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Shade cloth — for hot summers
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Jan 27 | Mar 2 | Apr 2 |
| First 32°F frost in fall is before | Dec 10 | Nov 20 | Nov 1 |
How to read it: in spring there is a 10% chance of a frost after April 2, so that is a safe date for tender plants. In fall there is a 10% chance of frost before November 1. A hard freeze (28°F) usually ends around January 23.
Hardiness zone by ZIP code in Windsor
- 95492 zone 9a
Nearby cities
- Healdsburg zone 9b, last frost Feb 15
- Santa Rosa zone 9b, last frost Feb 25
- Rohnert Park zone 9a, last frost Feb 28
- Petaluma zone 9a, last frost Feb 28
- Agua Caliente zone 9b, last frost Mar 2
- Sonoma zone 9b, last frost Mar 2
- Clearlake zone 9a, last frost Apr 10
- Novato zone 9b, last frost Jan 11
Questions
What growing zone is Windsor, CA?
Windsor is in USDA Plant Hardiness Zone 9a (average extreme winter low 20°F to 25°F), according to the USDA 2023 map.
When is the last frost in Windsor?
The average last spring frost (32°F) in Windsor is March 2. There is still a 10% chance of frost until April 2.
When can I plant tomatoes in Windsor?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Mar 9 – Mar 16. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Santa Rosa Sonoma Co Ap, CA (USW00023213), 4.8 km (3.0 mi) from the city center, elevation 35 m, based on 21 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.