Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for Walnut Creek, CA

Walnut Creek, CA is in USDA zone 9b across its 4 ZIP codes. The median last spring frost is March 8 and the first fall frost December 22.

Walnut Creek on the zone map

Outlined: its 4 ZIP code areas · 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

ZIP codes4

Last frostMar 8

First frostDec 22

Growing season282 days

9b 4 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 Walnut Creek, CA

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMarch 8median — 50% chance of a later frost

Safe for tender plantsApril 15only 10% chance of frost after

First fall frostDecember 22median — 10% chance by Nov 23

Growing season282 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 8 and returns around January 16.

From the NOAA station Mt Diablo Junction, CA, elevation 2,169 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 Walnut Creek

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 25 – Feb 8

SpinachSow outdoors · Jan 25 – Feb 15

Broccoli, cabbageStart indoors · Dec 28 – Jan 11

Broccoli, cabbageTransplant · Feb 15 – Mar 1

Onion setsPlant outdoors · Feb 8 – Feb 22

PotatoesPlant outdoors · Feb 15 – Mar 1

LettuceSow outdoors · Feb 8 – Feb 22

Carrots, beetsSow outdoors · Feb 15 – Mar 1

TomatoesStart indoors · Jan 11 – Jan 25

TomatoesTransplant · Mar 15 – Mar 29

Peppers, eggplantStart indoors · Dec 28 – Jan 11

Peppers, eggplantTransplant · Mar 22 – Apr 5

BeansSow outdoors · Mar 15 – Mar 29

Sweet cornSow outdoors · Mar 15 – Mar 29

Cucumbers, squashSow outdoors · Mar 15 – Mar 29

Fall lettuce, spinachSow outdoors · Oct 27 – Nov 10

GarlicPlant cloves · Dec 8 – Jan 12

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 8) and first fall frost (Dec 22) 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 94596 came on Jan 30 — about the same time as the 1991–2020 average (Jan 30).

average
Jan 302026
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 Walnut Creek, CA

The soil mapped at the center of ZIP 94596 is Lodo — clay loam, somewhat excessively drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH6.5neutral; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter3.5%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Lodo clay loam, 9 to 30 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 94596; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Walnut Creek, CA

Summer high83 °Faverage high, July

Winter low41 °Faverage low, December

Hot days27days a year at 90 °F or more

Freezing nights19nights a year at 32 °F or less

Growing degree days3,645base 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

Precipitation20.4 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mt Diablo Junction, CA (6 mi away); precipitation: Walnut Creek 1.4 Sse, CA (within 1 mile). Daylight is calculated from latitude.

ZIP codes in Walnut Creek

California planting zones →

Questions about Walnut Creek

What planting zone is Walnut Creek, CA?

Walnut Creek, CA is in USDA hardiness zone 9b on the 2023 map (9b: 25 to 30 °F).

When is the last frost in Walnut Creek, CA?

The median last spring frost is March 8 and the median first fall frost is December 22 (NOAA 1991–2020 normals, Mt Diablo Junction station).

When can I plant a garden in Walnut Creek, CA?

Cool-season crops like peas and spinach go in around Jan 25 – Feb 15; tomatoes, peppers, beans and squash after about Mar 15, once frost risk has passed.

What kind of onions grow in Walnut Creek, CA?

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

How much rain and snow does Walnut Creek, CA get?

About 20.4 inches of precipitation a year (NOAA 1991–2020 normals).