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

Planting zone for 94538 — Fremont, CA

ZIP code 94538 (Fremont, Alameda County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 94538 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 Fremont, 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 Newark, CA — 4 miles away, elevation 10 ft) the median growing season is 365 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 94538 came on Jan 25 — about the same time as the 1991–2020 average (Jan 27).

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 Fremont, CA

The soil mapped at the center of ZIP 94538 is Marvin — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH7.2neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter1.5%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Marvin silt loam, saline-alkali.

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 94538; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fremont, CA

Summer high77 °Faverage high, July
Winter low43 °Faverage low, January
Hot days10days a year at 90 °F or more
Freezing nights2nights a year at 32 °F or less
Growing degree days3,744base 50 °F — the season’s usable heat
Longest day14 h 45 mindaylight on June 21
Shortest day9 h 34 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation14.4 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°32 °FJanuary: average high 58 °F, low 43 °F 58°43° JanFebruary: average high 61 °F, low 46 °F 61°46° FebMarch: average high 65 °F, low 48 °F 65°48° MarApril: average high 67 °F, low 50 °F 67°50° AprMay: average high 71 °F, low 53 °F 71°53° MayJune: average high 75 °F, low 56 °F 75°56° JunJuly: average high 77 °F, low 58 °F 77°58° JulAugust: average high 77 °F, low 58 °F 77°58° AugSeptember: average high 77 °F, low 58 °F 77°58° SepOctober: average high 73 °F, low 54 °F 73°54° OctNovember: average high 65 °F, low 47 °F 65°47° NovDecember: average high 58 °F, low 43 °F 58°43° Dec

Precipitation by month inches

0″1″2″3″January: 2.77 in precipitation 2.8 JanFebruary: 2.82 in precipitation 2.8 FebMarch: 2.17 in precipitation 2.2 MarApril: 1.07 in precipitation 1.1 AprMay: 0.47 in precipitation 0.5 MayJune: 0.17 in precipitation 0.2 JunJuly: 0.00 in precipitation 0.0 JulAugust: 0.02 in precipitation 0.0 AugSeptember: 0.09 in precipitation 0.1 SepOctober: 0.65 in precipitation 0.7 OctNovember: 1.38 in precipitation 1.4 NovDecember: 2.76 in precipitation 2.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Newark, CA (4 mi away); precipitation: Newark, CA (4 mi away). 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.

945399b
Fremont, CA · 3 mi
9456010a
Newark, CA · 4 mi
945369b
Fremont, CA · 5 mi
9513410a
San Jose, CA · 5 mi
9500210a
Alviso, CA · 5 mi
9503610a
Milpitas, CA · 6 mi
9503510a
Milpitas, CA · 6 mi
9408910a
Sunnyvale, CA · 7 mi

All 5 ZIP codes in Fremont → · California planting zones →

Questions about 94538

What planting zone is ZIP code 94538?

ZIP code 94538 (Fremont, 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 94538 get?

About 14.4 inches of precipitation a year (NOAA 1991–2020 normals, Newark station).

How hot do summers get in Fremont, CA?

The average high peaks at 77 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 94538 have?

The USDA soil survey maps Marvin at the center of ZIP 94538: silt loam, somewhat poorly drained, pH about 7.2 (neutral).

Did spring come early in Fremont, CA in 2026?

Spring leaf-out near 94538 came on Jan 25 in 2026, about the same as the 1991–2020 average (Jan 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fremont, CA?

Intermediate onions: the longest day near 94538 is 14 h 45 min, so day-neutral types bulb best; long-day varieties may not bulb fully.