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

Planting zone for 95431 — Eldridge, CA

ZIP code 95431 (Eldridge, Sonoma County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is March 2 and the first fall frost November 27.

Where ZIP 95431 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 frostMar 2
First frostNov 27
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 Eldridge, 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 in Eldridge, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 2median — 50% chance of a later frost
Safe for tender plantsApril 5only 10% chance of frost after
First fall frostNovember 27median — 10% chance by Nov 6
Growing season270 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 20 and returns around December 14.

From the NOAA station Sonoma, CA — 4 miles away, elevation 98 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 95431

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 19 – Feb 2
SpinachSow outdoors · Jan 19 – Feb 9
Broccoli, cabbageStart indoors · Dec 22 – Jan 5
Broccoli, cabbageTransplant · Feb 9 – Feb 23
Onion setsPlant outdoors · Feb 2 – Feb 16
PotatoesPlant outdoors · Feb 9 – Feb 23
LettuceSow outdoors · Feb 2 – Feb 16
Carrots, beetsSow outdoors · Feb 9 – Feb 23
TomatoesStart indoors · Jan 5 – Jan 19
TomatoesTransplant · Mar 9 – Mar 23
Peppers, eggplantStart indoors · Dec 22 – Jan 5
Peppers, eggplantTransplant · Mar 16 – Mar 30
BeansSow outdoors · Mar 9 – Mar 23
Sweet cornSow outdoors · Mar 9 – Mar 23
Cucumbers, squashSow outdoors · Mar 9 – Mar 23
Fall lettuce, spinachSow outdoors · Oct 2 – Oct 16
GarlicPlant cloves · Nov 13 – Dec 18
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 2) and first fall frost (Nov 27) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 95431 came on Jan 27 — 3 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 Eldridge, CA

The soil mapped at the center of ZIP 95431 is Huichica — loam, moderately well drained.

TextureLoama good balance for most vegetables
pH5.3strongly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter1.25%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Huichica loam, 2 to 9 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 95431; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Eldridge, CA

Summer high86 °Faverage high, July
Winter low38 °Faverage low, January
Hot days44days a year at 90 °F or more
Freezing nights21nights a year at 32 °F or less
Growing degree days3,608base 50 °F — the season’s usable heat
Longest day14 h 50 mindaylight on June 21
Shortest day9 h 29 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation39.6 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 38 °F 57°38° JanFebruary: average high 62 °F, low 40 °F 62°40° FebMarch: average high 65 °F, low 42 °F 65°42° MarApril: average high 69 °F, low 44 °F 69°44° AprMay: average high 75 °F, low 48 °F 75°48° MayJune: average high 83 °F, low 51 °F 83°51° JunJuly: average high 86 °F, low 54 °F 86°54° JulAugust: average high 86 °F, low 53 °F 86°53° AugSeptember: average high 85 °F, low 51 °F 85°51° SepOctober: average high 78 °F, low 47 °F 78°47° OctNovember: average high 65 °F, low 42 °F 65°42° NovDecember: average high 57 °F, low 38 °F 57°38° Dec

Precipitation by month inches

0″2″4″6″8″January: 8.24 in precipitation 8.2 JanFebruary: 6.86 in precipitation 6.9 FebMarch: 6.26 in precipitation 6.3 MarApril: 2.18 in precipitation 2.2 AprMay: 1.56 in precipitation 1.6 MayJune: 0.38 in precipitation 0.4 JunJuly: 0.00 in precipitation 0.0 JulAugust: 0.06 in precipitation 0.1 AugSeptember: 0.14 in precipitation 0.1 SepOctober: 1.74 in precipitation 1.7 OctNovember: 3.93 in precipitation 3.9 NovDecember: 8.21 in precipitation 8.2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Sonoma, CA (4 mi away); precipitation: Glen Ellen 1.5 N, CA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

954429b
Glen Ellen, CA · 2 mi
954169b
Boyes Hot Springs, CA · 3 mi
954339b
El Verano, CA · 4 mi
954529b
Kenwood, CA · 6 mi
954879b
Vineburg, CA · 7 mi
954769b
Sonoma, CA · 7 mi
949519b
Penngrove, CA · 7 mi
945629b
Oakville, CA · 8 mi

California planting zones →

Questions about 95431

What planting zone is ZIP code 95431?

ZIP code 95431 (Eldridge, 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).

When is the last frost in Eldridge, CA?

The median last spring frost (32 °F) near 95431 is March 2; after April 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sonoma station.

When is the first frost in Eldridge, CA?

The median first fall frost near 95431 is November 27, giving a median frost-free growing season of 270 days.

When should I plant tomatoes in 95431?

Start tomato seeds indoors around Jan 5 – Jan 19 and set transplants outside around Mar 9 – Mar 23, one to three weeks after the median last frost.

How much rain and snow does 95431 get?

About 39.6 inches of precipitation a year (NOAA 1991–2020 normals, Glen Ellen 1.5 N station).

How hot do summers get in Eldridge, CA?

The average high peaks at 86 °F in July, with about 44 days a year at 90 °F or more.

What kind of soil does 95431 have?

The USDA soil survey maps Huichica at the center of ZIP 95431: loam, moderately well drained, pH about 5.3 (strongly acidic).

Did spring come early in Eldridge, CA in 2026?

Spring leaf-out near 95431 came on Jan 27 in 2026, 3 days earlier than the 1991–2020 average (Jan 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Eldridge, CA?

Intermediate onions: the longest day near 95431 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.