American Canyon, CA planting zone & frost dates
American Canyon is in USDA hardiness zone 9b. The last spring frost usually comes around March 5 and the first fall frost around November 21, for a growing season of about 256 days.
Planting calendar for American Canyon
Dates are counted from the average last spring frost (March 5) 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 8 – Jan 22 Transplant outdoors: Mar 12 – Mar 19 |
| Peppers | Start seeds indoors: Dec 25 – Jan 8 Transplant outdoors: Mar 19 – Mar 26 |
| Eggplant | Start seeds indoors: Dec 25 – Jan 8 Transplant outdoors: Mar 19 – Mar 26 |
| Broccoli | Start seeds indoors: Dec 25 – Jan 8 Transplant outdoors: Feb 5 – Feb 19 |
| Cabbage | Start seeds indoors: Dec 25 – Jan 8 Transplant outdoors: Feb 5 – Feb 19 |
| Onions (sets) | Plant outdoors: Feb 5 – Feb 19 |
| Peas | Sow outdoors: Jan 22 – Feb 5 |
| Spinach | Sow outdoors: Jan 22 – Feb 5 |
| Lettuce | Sow outdoors: Feb 5 – Feb 19 |
| Carrots | Sow outdoors: Feb 5 – Feb 19 |
| Potatoes | Plant outdoors: Feb 5 – Feb 19 |
| Beans | Sow outdoors: Mar 12 – Mar 19 |
| Sweet corn | Sow outdoors: Mar 12 – Mar 19 |
| Cucumbers | Sow outdoors: Mar 12 – Mar 19 |
| Squash & zucchini | Sow outdoors: Mar 12 – Mar 19 |
| Basil | Start seeds indoors: Jan 22 – Feb 5 Transplant outdoors: Mar 12 – Mar 19 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 26 (8 weeks before the average first fall frost on Nov 21).
Useful for zone 9b 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 26 | Mar 5 | Apr 16 |
| First 32°F frost in fall is before | Dec 13 | Nov 21 | Nov 3 |
How to read it: in spring there is a 10% chance of a frost after April 16, so that is a safe date for tender plants. In fall there is a 10% chance of frost before November 3. A hard freeze (28°F) usually ends around January 23.
Hardiness zone by ZIP code in American Canyon
- 94503 zone 9b
Nearby cities
Questions
What growing zone is American Canyon, CA?
American Canyon 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 American Canyon?
The average last spring frost (32°F) in American Canyon is March 5. There is still a 10% chance of frost until April 16.
When can I plant tomatoes in American Canyon?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Mar 12 – Mar 19. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Napa Co Ap, CA (USW00093227), 4.5 km (2.8 mi) from the city center, elevation 4 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.