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

Planting zone for 94581 — Napa, CA

ZIP code 94581 (Napa, Napa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is February 12 and the first fall frost December 4.

Where ZIP 94581 is

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 frostFeb 12
First frostDec 4
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 Napa, 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 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 — 2 miles away, 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 94581

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).

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

30°40°50°60°70°80°90°32 °FJanuary: average high 59 °F, low 40 °F 59°40° JanFebruary: average high 63 °F, low 42 °F 63°42° FebMarch: average high 68 °F, low 44 °F 68°44° MarApril: average high 72 °F, low 46 °F 72°46° AprMay: average high 77 °F, low 50 °F 77°50° MayJune: average high 82 °F, low 54 °F 82°54° JunJuly: average high 83 °F, low 56 °F 83°56° JulAugust: average high 84 °F, low 56 °F 84°56° AugSeptember: average high 84 °F, low 53 °F 84°53° SepOctober: average high 78 °F, low 49 °F 78°49° OctNovember: average high 66 °F, low 44 °F 66°44° NovDecember: average high 59 °F, low 40 °F 59°40° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 4.98 in precipitation 5.0 JanFebruary: 5.13 in precipitation 5.1 FebMarch: 3.67 in precipitation 3.7 MarApril: 1.72 in precipitation 1.7 AprMay: 1.08 in precipitation 1.1 MayJune: 0.29 in precipitation 0.3 JunJuly: 0.00 in precipitation 0.0 JulAugust: 0.06 in precipitation 0.1 AugSeptember: 0.09 in precipitation 0.1 SepOctober: 1.34 in precipitation 1.3 OctNovember: 2.77 in precipitation 2.8 NovDecember: 5.53 in precipitation 5.5 Dec

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.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

945599b
Napa, CA · 3 mi
945589b
Napa, CA · 8 mi
945039b
American Canyon, CA · 8 mi
954879b
Vineburg, CA · 8 mi
945999b
Yountville, CA · 9 mi
945349b
Fairfield, CA · 10 mi
954769b
Sonoma, CA · 10 mi
954169b
Boyes Hot Springs, CA · 11 mi

All 3 ZIP codes in Napa → · California planting zones →

Questions about 94581

What planting zone is ZIP code 94581?

ZIP code 94581 (Napa, 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 Napa, CA?

The median last spring frost (32 °F) near 94581 is February 12; after March 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Napa State Hospital station.

When is the first frost in Napa, CA?

The median first fall frost near 94581 is December 4, giving a median frost-free growing season of 299 days.

When should I plant tomatoes in 94581?

Start tomato seeds indoors around Dec 18 – Jan 1 and set transplants outside around Feb 19 – Mar 5, one to three weeks after the median last frost.

How much rain and snow does 94581 get?

About 26.7 inches of precipitation a year (NOAA 1991–2020 normals, Napa State Hospital station).

How hot do summers get in Napa, CA?

The average high peaks at 84 °F in August, with about 32 days a year at 90 °F or more.

What kind of soil does 94581 have?

The USDA soil survey maps Cole at the center of ZIP 94581: silt loam, somewhat poorly drained, pH about 6.5 (neutral).

Did spring come early in Napa, CA in 2026?

Spring leaf-out near 94581 came on Jan 29 in 2026, about the same as the 1991–2020 average (Jan 31), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Napa, CA?

Intermediate onions: the longest day near 94581 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.