Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 94941 — Mill Valley, CA

ZIP code 94941 (Mill Valley, Marin County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 94941 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not 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.

Zone10a30 to 35 °F
Coldest night−1.1 to 1.7 °C
Last frostrare
First frostrare
2012 zone10a

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 Service

Loading 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 94941 came on Jan 24 — 6 days earlier than the 1991–2020 average (Jan 30).

JanFebMarAprMayJun

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 soil mapped at the center of ZIP 94941 is Maymen — gravelly loam, somewhat excessively drained.

TextureGravelly loama good balance for most vegetables
pH5.5moderately acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Maymen-Maymen variant gravelly loams, 30 to 75 percent slopes.

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 94941; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mill Valley, CA

Summer high83 °Faverage high, July
Winter low42 °Faverage low, January
Hot days27days a year at 90 °F or more
Freezing nights5nights a year at 32 °F or less
Growing degree days3,578base 50 °F — the season’s usable heat
Longest day14 h 48 mindaylight on June 21
Shortest day9 h 32 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation36.2 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°32 °FJanuary: average high 57 °F, low 42 °F 57°42° JanFebruary: average high 61 °F, low 43 °F 61°43° FebMarch: average high 65 °F, low 44 °F 65°44° MarApril: average high 69 °F, low 46 °F 69°46° AprMay: average high 74 °F, low 50 °F 74°50° MayJune: average high 80 °F, low 52 °F 80°52° JunJuly: average high 83 °F, low 53 °F 83°53° JulAugust: average high 83 °F, low 54 °F 83°54° AugSeptember: average high 82 °F, low 53 °F 82°53° SepOctober: average high 76 °F, low 50 °F 76°50° OctNovember: average high 64 °F, low 45 °F 64°45° NovDecember: average high 56 °F, low 42 °F 56°42° Dec

Precipitation by month inches

0″2″4″6″8″January: 6.62 in precipitation 6.6 JanFebruary: 6.84 in precipitation 6.8 FebMarch: 4.58 in precipitation 4.6 MarApril: 2.27 in precipitation 2.3 AprMay: 1.37 in precipitation 1.4 MayJune: 0.48 in precipitation 0.5 JunJuly: 0.03 in precipitation 0.0 JulAugust: 0.11 in precipitation 0.1 AugSeptember: 0.19 in precipitation 0.2 SepOctober: 1.69 in precipitation 1.7 OctNovember: 4.20 in precipitation 4.2 NovDecember: 7.86 in precipitation 7.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kentfield, CA (4 mi away); precipitation: Muir Woods, CA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

3 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

949149b
Kentfield, CA · 3 mi
949049b
Greenbrae, CA · 3 mi
9493010a
Fairfax, CA · 3 mi
9497010a
Stinson Beach, CA · 3 mi
9494210a
Mill Valley, CA · 3 mi
949579b
Ross, CA · 3 mi
9497710a
Larkspur, CA · 4 mi
9493910a
Larkspur, CA · 4 mi

All 2 ZIP codes in Mill Valley → · California planting zones →

Questions about 94941

What planting zone is ZIP code 94941?

ZIP code 94941 (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 94941 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.

What kind of soil does 94941 have?

The USDA soil survey maps Maymen at the center of ZIP 94941: gravelly loam, somewhat excessively drained, pH about 5.5 (moderately acidic).

Did spring come early in Mill Valley, CA in 2026?

Spring leaf-out near 94941 came on Jan 24 in 2026, 6 days earlier than the 1991–2020 average (Jan 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mill Valley, CA?

Intermediate onions: the longest day near 94941 is 14 h 48 min, so day-neutral types bulb best; long-day varieties may not bulb fully.