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

Planting zone for 94558 — Napa, CA

ZIP code 94558 (Napa, Napa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is March 6 and the first fall frost November 30.

Where ZIP 94558 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 6
First frostNov 30
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 frostMarch 6median — 50% chance of a later frost
Safe for tender plantsApril 6only 10% chance of frost after
First fall frostNovember 30median — 10% chance by Nov 12
Growing season266 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 22 and returns around December 15.

From the NOAA station Markley Cove, CA — 8 miles away, elevation 479 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 94558

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 23 – Feb 6
SpinachSow outdoors · Jan 23 – Feb 13
Broccoli, cabbageStart indoors · Dec 26 – Jan 9
Broccoli, cabbageTransplant · Feb 13 – Feb 27
Onion setsPlant outdoors · Feb 6 – Feb 20
PotatoesPlant outdoors · Feb 13 – Feb 27
LettuceSow outdoors · Feb 6 – Feb 20
Carrots, beetsSow outdoors · Feb 13 – Feb 27
TomatoesStart indoors · Jan 9 – Jan 23
TomatoesTransplant · Mar 13 – Mar 27
Peppers, eggplantStart indoors · Dec 26 – Jan 9
Peppers, eggplantTransplant · Mar 20 – Apr 3
BeansSow outdoors · Mar 13 – Mar 27
Sweet cornSow outdoors · Mar 13 – Mar 27
Cucumbers, squashSow outdoors · Mar 13 – Mar 27
Fall lettuce, spinachSow outdoors · Oct 5 – Oct 19
GarlicPlant cloves · Nov 16 – Dec 21
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 6) and first fall frost (Nov 30) 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 94558 came on Jan 31 — 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 94558 is Bressa — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.75%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Bressa-Dibble complex, 30 to 50 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 94558; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Napa, CA

Summer high95 °Faverage high, July
Winter low36 °Faverage low, January
Hot days91days a year at 90 °F or more
Freezing nights24nights a year at 32 °F or less
Growing degree days4,273base 50 °F — the season’s usable heat
Longest day14 h 51 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
Precipitation27.9 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 57 °F, low 36 °F 57°36° JanFebruary: average high 61 °F, low 38 °F 61°38° FebMarch: average high 66 °F, low 40 °F 66°40° MarApril: average high 71 °F, low 43 °F 71°43° AprMay: average high 79 °F, low 49 °F 79°49° MayJune: average high 88 °F, low 54 °F 88°54° JunJuly: average high 95 °F, low 57 °F 95°57° JulAugust: average high 94 °F, low 56 °F 94°56° AugSeptember: average high 90 °F, low 53 °F 90°53° SepOctober: average high 79 °F, low 47 °F 79°47° OctNovember: average high 66 °F, low 41 °F 66°41° NovDecember: average high 58 °F, low 36 °F 58°36° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 5.72 in precipitation 5.7 JanFebruary: 5.93 in precipitation 5.9 FebMarch: 4.10 in precipitation 4.1 MarApril: 1.67 in precipitation 1.7 AprMay: 1.01 in precipitation 1.0 MayJune: 0.23 in precipitation 0.2 JunJuly: 0.01 in precipitation 0.0 JulAugust: 0.03 in precipitation 0.0 AugSeptember: 0.07 in precipitation 0.1 SepOctober: 1.09 in precipitation 1.1 OctNovember: 2.49 in precipitation 2.5 NovDecember: 5.60 in precipitation 5.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Markley Cove, CA (8 mi away); precipitation: Markley Cove, CA (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

945819b
Napa, CA · 8 mi
956889b
Vacaville, CA · 9 mi
956969b
Vacaville, CA · 10 mi
945999b
Yountville, CA · 10 mi
945349b
Fairfield, CA · 11 mi
945599b
Napa, CA · 11 mi
945629b
Oakville, CA · 12 mi
945339b
Fairfield, CA · 12 mi

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

Questions about 94558

What planting zone is ZIP code 94558?

ZIP code 94558 (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 94558 is March 6; after April 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Markley Cove station.

When is the first frost in Napa, CA?

The median first fall frost near 94558 is November 30, giving a median frost-free growing season of 266 days.

When should I plant tomatoes in 94558?

Start tomato seeds indoors around Jan 9 – Jan 23 and set transplants outside around Mar 13 – Mar 27, one to three weeks after the median last frost.

How much rain and snow does 94558 get?

About 27.9 inches of precipitation a year (NOAA 1991–2020 normals, Markley Cove station).

How hot do summers get in Napa, CA?

The average high peaks at 95 °F in July, with about 91 days a year at 90 °F or more.

What kind of soil does 94558 have?

The USDA soil survey maps Bressa at the center of ZIP 94558: silt loam, well drained, pH about 6.7 (neutral).

Did spring come early in Napa, CA in 2026?

Spring leaf-out near 94558 came on Jan 31 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 94558 is 14 h 51 min, so day-neutral types bulb best; long-day varieties may not bulb fully.