When to plant in Mill Valley, CA
USDA Zone 10aMill Valley, California frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
Mill Valley enjoys a long ~336-day frost-free season — you can succession-sow, fit in a second crop, and grow long-season heat-lovers with room to spare. Zone 10a is warm enough that Mill Valley can grow subtropical perennials, and the short (or absent) frost period barely limits the annual calendar.
The average last spring frost in Mill Valley is now 10 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
KENTFIELD · 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 Mill Valley’s own odds, recorded at KENTFIELD.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Apr 5 | Mar 5 | Jan 29 | Nov 12 | Nov 29 | Dec 21 |
| 32°F | Feb 25 | Jan 16 | Dec 21 | Nov 30 | Dec 18 | Jan 19 |
| 28°F | Jan 23 | Dec 30 | Dec 9 | Dec 4 | Dec 24 | Jan 21 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Nothing new to sow or transplant outdoors in the next few weeks — a seasonal lull. Check the full-year calendar below for the next window.
Full-year planting calendar
Each bar is the exact window to take a planting action in Mill Valley, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 15 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.
Mill Valley planting FAQ
When is the last spring frost in Mill Valley, CA?
Mill Valley's average last spring frost falls near January 16 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Mill Valley, CA?
The first fall frost in Mill Valley typically arrives around December 18 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Mill Valley in?
Mill Valley is in USDA hardiness zone 10a. In zone 10a, winters are mild — many tender perennials overwinter here.
How long is the growing season in Mill Valley?
There are roughly 336 frost-free days in Mill Valley (a long growing season), running from the average last frost around January 16 to the first fall frost near December 18.
When should I plant tomatoes in Mill Valley?
In Mill Valley, start tomato seeds indoors around November 21–December 5, then transplant seedlings outdoors around January 23 once the danger of frost has passed.
Never miss a window in Mill Valley
An email when it’s time to start seeds, transplant, and sow — timed to Mill Valley’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Tamalpais-Homestead Valley · 3 km
- Larkspur · 4 km
- Corte Madera · 4 km
- San Anselmo · 9 km
- San Rafael · 9 km
- Richmond · 17 km
- San Pablo · 19 km
- Novato · 20 km
Frost dates recorded at KENTFIELD, 5 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 Mill Valley, CA — Frost Dates & Zone 10a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00044500. Retrieved from https://blissgarden.com/california/mill-valley.