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

Planting zone for Napa, CA

Napa, CA is in USDA zone 9b across its 3 ZIP codes. The median last spring frost is February 12 and the first fall frost December 4.

Napa on the zone map

Outlined: its 2 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 codes3

Last frostFeb 12

First frostDec 4

Growing season299 days

9b 3 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 Napa, CA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostFebruary 12median — 50% chance of a later frost

Safe for tender plantsMarch 13only 10% chance of frost after

First fall frostDecember 4median — 10% chance by Nov 15

Growing season299 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 11 and returns around December 19.

From the NOAA station Napa State Hospital, CA, elevation 36 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 Napa

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 1 – Jan 15

SpinachSow outdoors · Jan 1 – Jan 22

Broccoli, cabbageStart indoors · Dec 4 – Dec 18

Broccoli, cabbageTransplant · Jan 22 – Feb 5

Onion setsPlant outdoors · Jan 15 – Jan 29

PotatoesPlant outdoors · Jan 22 – Feb 5

LettuceSow outdoors · Jan 15 – Jan 29

Carrots, beetsSow outdoors · Jan 22 – Feb 5

TomatoesStart indoors · Dec 18 – Jan 1

TomatoesTransplant · Feb 19 – Mar 5

Peppers, eggplantStart indoors · Dec 4 – Dec 18

Peppers, eggplantTransplant · Feb 26 – Mar 12

BeansSow outdoors · Feb 19 – Mar 5

Sweet cornSow outdoors · Feb 19 – Mar 5

Cucumbers, squashSow outdoors · Feb 19 – Mar 5

Fall lettuce, spinachSow outdoors · Oct 9 – Oct 23

GarlicPlant cloves · Nov 20 – Dec 25

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 12) and first fall frost (Dec 4) 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 94581 came on Jan 29 — about the same time as the 1991–2020 average (Jan 31).

average
Jan 312026
Jan 29

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 Napa, CA

The soil mapped at the center of ZIP 94581 is Cole — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables

pH6.5neutral; most vegetables like 6.0–7.0

DrainageSomewhat poorly drainedconsider raised beds

Organic matter4%moderate

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Cole silt loam, 0 to 2 percent slopes, MLRA 14.

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 94581; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Napa, CA

Summer high84 °Faverage high, August

Winter low40 °Faverage low, January

Hot days32days a year at 90 °F or more

Freezing nights13nights a year at 32 °F or less

Growing degree days3,959base 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

Precipitation26.7 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: Napa State Hospital, CA (2 mi away); precipitation: Napa State Hospital, CA (2 mi away). Daylight is calculated from latitude.

ZIP codes in Napa

California planting zones →

Questions about Napa

What planting zone is Napa, CA?

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

When is the last frost in Napa, CA?

The median last spring frost is February 12 and the median first fall frost is December 4 (NOAA 1991–2020 normals, Napa State Hospital station).

When can I plant a garden in Napa, CA?

Cool-season crops like peas and spinach go in around Jan 1 – Jan 22; tomatoes, peppers, beans and squash after about Feb 19, once frost risk has passed.

What kind of onions grow in Napa, CA?

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

How much rain and snow does Napa, CA get?

About 26.7 inches of precipitation a year (NOAA 1991–2020 normals).