Planting zone for 94942 — Mill Valley, CA
ZIP code 94942 (Mill Valley, Marin County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.
Where ZIP 94942 is
tap the map for the zone at any spot · scroll or pinch to zoomNot the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.
Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 10a means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Mill Valley, CA…
Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.
Frost dates
A 32 °F frost doesn't happen here in most winters. At the nearest station (NOAA station Kentfield, CA — 4 miles away, elevation 144 ft) the median growing season is 334 days. When frost does come, it is a midwinter night or two; cover tender plants when a freeze is forecast.
Frost data: NOAA NCEI U.S. Climate Normals 1991–2020.
When spring arrived in 2026
In 2026, spring leaf-out near 94942 came on Jan 26 — about the same time as the 1991–2020 average (Jan 28).
Jan 282026
Jan 26
The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).
Soil in Mill Valley, CA
The center of ZIP 94942 is mapped as Xerorthents-Urban land complex, 0 to 9 percent slopes: built-over ground without natural soil data. Garden soil here is usually imported or disturbed — test before you plant.
Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 94942; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Mill Valley, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kentfield, CA (4 mi away); precipitation: Muir Woods, CA (within 1 mile). Daylight is calculated from latitude.
Nearby ZIP codes
2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.
All 2 ZIP codes in Mill Valley → · California planting zones →
Questions about 94942
What planting zone is ZIP code 94942?
ZIP code 94942 (Mill Valley, CA) is in USDA hardiness zone 10a on the 2023 map: the coldest night of an average winter reaches 30 to 35 °F (−1.1 to 1.7 °C).
How much rain and snow does 94942 get?
About 36.2 inches of precipitation a year (NOAA 1991–2020 normals, Muir Woods station).
How hot do summers get in Mill Valley, CA?
The average high peaks at 83 °F in July, with about 27 days a year at 90 °F or more.
Did spring come early in Mill Valley, CA in 2026?
Spring leaf-out near 94942 came on Jan 26 in 2026, about the same as the 1991–2020 average (Jan 28), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Mill Valley, CA?
Intermediate onions: the longest day near 94942 is 14 h 48 min, so day-neutral types bulb best; long-day varieties may not bulb fully.