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

Planting zone for 94534 — Fairfield, CA

ZIP code 94534 (Fairfield, Solano County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F.

Where ZIP 94534 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.

Zone9b25 to 30 °F
Coldest night−3.9 to −1.1 °C
Last frostrare
First frostrare
2012 zone9b

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 9b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Fairfield, 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 Fairfield, CA — 4 miles away, elevation 39 ft) the median growing season is 336 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 94534 came on Jan 29 — about the same time as 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 Fairfield, CA

The soil mapped at the center of ZIP 94534 is Brentwood — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH7.0neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Brentwood clay loam, 0 to 2 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 94534; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fairfield, CA

Summer high90 °Faverage high, July
Winter low40 °Faverage low, January
Hot days60days a year at 90 °F or more
Freezing nights8nights a year at 32 °F or less
Growing degree days4,507base 50 °F — the season’s usable heat
Longest day14 h 50 mindaylight on June 21
Shortest day9 h 30 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation26.1 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°32 °FJanuary: average high 57 °F, low 40 °F 57°40° JanFebruary: average high 62 °F, low 43 °F 62°43° FebMarch: average high 66 °F, low 45 °F 66°45° MarApril: average high 71 °F, low 48 °F 71°48° AprMay: average high 78 °F, low 52 °F 78°52° MayJune: average high 85 °F, low 56 °F 85°56° JunJuly: average high 90 °F, low 58 °F 90°58° JulAugust: average high 89 °F, low 58 °F 89°58° AugSeptember: average high 87 °F, low 57 °F 87°57° SepOctober: average high 78 °F, low 52 °F 78°52° OctNovember: average high 66 °F, low 45 °F 66°45° NovDecember: average high 57 °F, low 40 °F 57°40° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 5.30 in precipitation 5.3 JanFebruary: 5.24 in precipitation 5.2 FebMarch: 3.86 in precipitation 3.9 MarApril: 1.49 in precipitation 1.5 AprMay: 1.04 in precipitation 1.0 MayJune: 0.21 in precipitation 0.2 JunJuly: 0.00 in precipitation 0.0 JulAugust: 0.03 in precipitation 0.0 AugSeptember: 0.07 in precipitation 0.1 SepOctober: 1.04 in precipitation 1.0 OctNovember: 2.40 in precipitation 2.4 NovDecember: 5.41 in precipitation 5.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Fairfield, CA (4 mi away); precipitation: Fairfield 5.9 Wsw, CA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

945339b
Fairfield, CA · 7 mi
945039b
American Canyon, CA · 7 mi
945109b
Benicia, CA · 9 mi
945919b
Vallejo, CA · 9 mi
945599b
Napa, CA · 10 mi
945819b
Napa, CA · 10 mi
945899b
Vallejo, CA · 10 mi
945359b
Travis Afb, CA · 10 mi

All 2 ZIP codes in Fairfield → · California planting zones →

Questions about 94534

What planting zone is ZIP code 94534?

ZIP code 94534 (Fairfield, CA) is in USDA hardiness zone 9b on the 2023 map: the coldest night of an average winter reaches 25 to 30 °F (−3.9 to −1.1 °C).

How much rain and snow does 94534 get?

About 26.1 inches of precipitation a year (NOAA 1991–2020 normals, Fairfield 5.9 Wsw station).

How hot do summers get in Fairfield, CA?

The average high peaks at 90 °F in July, with about 60 days a year at 90 °F or more.

What kind of soil does 94534 have?

The USDA soil survey maps Brentwood at the center of ZIP 94534: clay loam, well drained, pH about 7.0 (neutral).

Did spring come early in Fairfield, CA in 2026?

Spring leaf-out near 94534 came on Jan 29 in 2026, about the same as the 1991–2020 average (Jan 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fairfield, CA?

Intermediate onions: the longest day near 94534 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.