Mill Valley, CA planting zone & frost dates
Mill Valley is in USDA hardiness zone 10a. The last spring frost usually comes around January 16 and the first fall frost around December 18, for a growing season of about 334 days.
Planting calendar for Mill Valley
Dates are counted from the average last spring frost (January 16) 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: Nov 21 – Dec 5 Transplant outdoors: Jan 23 – Jan 30 |
| Peppers | Start seeds indoors: Nov 7 – Nov 21 Transplant outdoors: Jan 30 – Feb 6 |
| Eggplant | Start seeds indoors: Nov 7 – Nov 21 Transplant outdoors: Jan 30 – Feb 6 |
| Broccoli | Start seeds indoors: Nov 7 – Nov 21 Transplant outdoors: Dec 19 – Jan 2 |
| Cabbage | Start seeds indoors: Nov 7 – Nov 21 Transplant outdoors: Dec 19 – Jan 2 |
| Onions (sets) | Plant outdoors: Dec 19 – Jan 2 |
| Peas | Sow outdoors: Dec 5 – Dec 19 |
| Spinach | Sow outdoors: Dec 5 – Dec 19 |
| Lettuce | Sow outdoors: Dec 19 – Jan 2 |
| Carrots | Sow outdoors: Dec 19 – Jan 2 |
| Potatoes | Plant outdoors: Dec 19 – Jan 2 |
| Beans | Sow outdoors: Jan 23 – Jan 30 |
| Sweet corn | Sow outdoors: Jan 23 – Jan 30 |
| Cucumbers | Sow outdoors: Jan 23 – Jan 30 |
| Squash & zucchini | Sow outdoors: Jan 23 – Jan 30 |
| Basil | Start seeds indoors: Dec 5 – Dec 19 Transplant outdoors: Jan 23 – Jan 30 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Oct 23 (8 weeks before the average first fall frost on Dec 18).
Useful for zone 10a 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 | Dec 21 | Jan 16 | Feb 25 |
| First 32°F frost in fall is before | Jan 19 | Dec 18 | Nov 30 |
How to read it: in spring there is a 10% chance of a frost after February 25, so that is a safe date for tender plants. In fall there is a 10% chance of frost before November 30. A hard freeze (28°F) usually ends around December 30.
Hardiness zone by ZIP code in Mill Valley
- 94941 zone 10a
- 94942 zone 10a
Nearby cities
- Tamalpais-Homestead Valley zone 10a, last frost Jan 16
- Larkspur zone 10a, last frost Jan 16
- San Rafael zone 10a, last frost Jan 16
- San Anselmo zone 9b, last frost Jan 16
- San Francisco zone 10b
- Richmond zone 10a
- Novato zone 9b, last frost Jan 11
- San Pablo zone 10a
Questions
What growing zone is Mill Valley, CA?
Mill Valley is in USDA Plant Hardiness Zone 10a (average extreme winter low 30°F to 35°F), according to the USDA 2023 map.
When is the last frost in Mill Valley?
The average last spring frost (32°F) in Mill Valley is January 16. There is still a 10% chance of frost until February 25.
When can I plant tomatoes in Mill Valley?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Jan 23 – Jan 30. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Kentfield, CA (USC00044500), 5.6 km (3.5 mi) from the city center, elevation 44 m, based on 27 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.