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

Planting zone for Palo Alto, CA

Palo Alto, CA is in USDA zones 9b to 10a across its 6 ZIP codes. The median last spring frost is February 1 and the first fall frost December 7.

Palo Alto 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.

Zones9b–10a25 to 35 °F

ZIP codes6

Last frostFeb 1

First frostDec 7

Growing season310 days

9b 5 ZIPs 10a 1 ZIP

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 Palo Alto, CA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostFebruary 1median — 50% chance of a later frost

Safe for tender plantsMarch 4only 10% chance of frost after

First fall frostDecember 7median — 10% chance by Nov 20

Growing season310 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 4 and returns around December 22.

From the NOAA station Palo Alto, CA, elevation 26 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 Palo Alto

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Dec 21 – Jan 4

SpinachSow outdoors · Dec 21 – Jan 11

Broccoli, cabbageStart indoors · Nov 23 – Dec 7

Broccoli, cabbageTransplant · Jan 11 – Jan 25

Onion setsPlant outdoors · Jan 4 – Jan 18

PotatoesPlant outdoors · Jan 11 – Jan 25

LettuceSow outdoors · Jan 4 – Jan 18

Carrots, beetsSow outdoors · Jan 11 – Jan 25

TomatoesStart indoors · Dec 7 – Dec 21

TomatoesTransplant · Feb 8 – Feb 22

Peppers, eggplantStart indoors · Nov 23 – Dec 7

Peppers, eggplantTransplant · Feb 15 – Mar 1

BeansSow outdoors · Feb 8 – Feb 22

Sweet cornSow outdoors · Feb 8 – Feb 22

Cucumbers, squashSow outdoors · Feb 8 – Feb 22

Fall lettuce, spinachSow outdoors · Oct 12 – Oct 26

GarlicPlant cloves · Nov 23 – Dec 28

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 1) and first fall frost (Dec 7) 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 94302 came on Jan 27 — about the same time as the 1991–2020 average (Jan 28).

average
Jan 282026
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 Palo Alto, CA

The soil mapped at the center of ZIP 94302 is Flaskan — sandy loam, well drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureSandy loamdrains and warms fast; dries out and needs more feeding

pH6.4slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Urban land-Flaskan complex, 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 94302; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Palo Alto, CA

Summer high80 °Faverage high, September

Winter low39 °Faverage low, January

Hot days12days a year at 90 °F or more

Freezing nights14nights a year at 32 °F or less

Growing degree days3,364base 50 °F — the season’s usable heat

Longest day14 h 45 mindaylight on June 21

Shortest day9 h 35 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation15.1 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: Palo Alto, CA (within 1 mile); precipitation: Palo Alto, CA (within 1 mile). Daylight is calculated from latitude.

ZIP codes in Palo Alto

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Questions about Palo Alto

What planting zone is Palo Alto, CA?

Palo Alto, CA is in USDA hardiness zones 9b to 10a on the 2023 map (9b: 25 to 30 °F; 10a: 30 to 35 °F).

When is the last frost in Palo Alto, CA?

The median last spring frost is February 1 and the median first fall frost is December 7 (NOAA 1991–2020 normals, Palo Alto station).

When can I plant a garden in Palo Alto, CA?

Cool-season crops like peas and spinach go in around Dec 21 – Jan 11; tomatoes, peppers, beans and squash after about Feb 8, once frost risk has passed.

What kind of onions grow in Palo Alto, CA?

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

How much rain and snow does Palo Alto, CA get?

About 15.1 inches of precipitation a year (NOAA 1991–2020 normals).