Sonoma, CA planting zone & frost dates
Sonoma is in USDA hardiness zone 9b. The last spring frost usually comes around March 2 and the first fall frost around November 27, for a growing season of about 270 days.
Planting calendar for Sonoma
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 Oct 2 (8 weeks before the average first fall frost on Nov 27).
Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Jan 27 | Mar 2 | Apr 5 |
| First 32°F frost in fall is before | Dec 21 | Nov 27 | Nov 6 |
How to read it: in spring there is a 10% chance of a frost after April 5, so that is a safe date for tender plants. In fall there is a 10% chance of frost before November 6. A hard freeze (28°F) usually ends around January 20.
Hardiness zone by ZIP code in Sonoma
- 95476 zone 9b
Nearby cities
- Agua Caliente zone 9b, last frost Mar 2
- Napa zone 9b, last frost Feb 12
- Petaluma zone 9a, last frost Feb 28
- Novato zone 9b, last frost Jan 11
- American Canyon zone 9b, last frost Mar 5
- Rohnert Park zone 9a, last frost Feb 28
- Vallejo zone 9b, last frost Jan 17
- Santa Rosa zone 9b, last frost Feb 25
Questions
What growing zone is Sonoma, CA?
Sonoma is in USDA Plant Hardiness Zone 9b (average extreme winter low 25°F to 30°F), according to the USDA 2023 map.
When is the last frost in Sonoma?
The average last spring frost (32°F) in Sonoma is March 2. There is still a 10% chance of frost until April 5.
When can I plant tomatoes in Sonoma?
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 Sonoma, CA (USC00048351), 0.9 km (0.6 mi) from the city center, elevation 30 m, based on 30 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.