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

Planting zone for 94508 — Angwin, CA

ZIP code 94508 (Angwin, Napa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is April 7 and the first fall frost December 5.

Where ZIP 94508 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 frostApr 7
First frostDec 5
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 Angwin, 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 Angwin, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 7median — 50% chance of a later frost
Safe for tender plantsApril 30only 10% chance of frost after
First fall frostDecember 5median — 10% chance by Nov 14
Growing season245 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 18 and returns around December 30.

From the NOAA station Angwin Pacific Union College, CA — within 1 mile, elevation 1,716 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 94508

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 24 – Mar 10
SpinachSow outdoors · Feb 24 – Mar 17
Broccoli, cabbageStart indoors · Jan 27 – Feb 10
Broccoli, cabbageTransplant · Mar 17 – Mar 31
Onion setsPlant outdoors · Mar 10 – Mar 24
PotatoesPlant outdoors · Mar 17 – Mar 31
LettuceSow outdoors · Mar 10 – Mar 24
Carrots, beetsSow outdoors · Mar 17 – Mar 31
TomatoesStart indoors · Feb 10 – Feb 24
TomatoesTransplant · Apr 14 – Apr 28
Peppers, eggplantStart indoors · Jan 27 – Feb 10
Peppers, eggplantTransplant · Apr 21 – May 5
BeansSow outdoors · Apr 14 – Apr 28
Sweet cornSow outdoors · Apr 14 – Apr 28
Cucumbers, squashSow outdoors · Apr 14 – Apr 28
Fall lettuce, spinachSow outdoors · Oct 10 – Oct 24
GarlicPlant cloves · Nov 21 – Dec 26
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 7) and first fall frost (Dec 5) 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 94508 came on Jan 20 — 12 days earlier than the 1991–2020 average (Feb 1).

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 Angwin, CA

The soil mapped at the center of ZIP 94508 is Aiken — loam, well drained.

TextureLoama good balance for most vegetables
pH5.8moderately acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter5%high
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Aiken loam, 2 to 15 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 94508; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Angwin, CA

Summer high85 °Faverage high, July
Winter low39 °Faverage low, January
Hot days27days a year at 90 °F or more
Freezing nights15nights a year at 32 °F or less
Growing degree days3,278base 50 °F — the season’s usable heat
Longest day14 h 52 mindaylight on June 21
Shortest day9 h 28 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation39.7 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°32 °FJanuary: average high 54 °F, low 39 °F 54°39° JanFebruary: average high 56 °F, low 40 °F 56°40° FebMarch: average high 60 °F, low 41 °F 60°41° MarApril: average high 66 °F, low 42 °F 66°42° AprMay: average high 73 °F, low 47 °F 73°47° MayJune: average high 80 °F, low 51 °F 80°51° JunJuly: average high 85 °F, low 54 °F 85°54° JulAugust: average high 84 °F, low 54 °F 84°54° AugSeptember: average high 81 °F, low 53 °F 81°53° SepOctober: average high 72 °F, low 50 °F 72°50° OctNovember: average high 60 °F, low 43 °F 60°43° NovDecember: average high 53 °F, low 39 °F 53°39° Dec

Precipitation by month inches

0″2″4″6″8″January: 7.80 in precipitation 7.8 JanFebruary: 7.59 in precipitation 7.6 FebMarch: 5.50 in precipitation 5.5 MarApril: 2.37 in precipitation 2.4 AprMay: 1.56 in precipitation 1.6 MayJune: 0.36 in precipitation 0.4 JunJuly: 0.01 in precipitation 0.0 JulAugust: 0.04 in precipitation 0.0 AugSeptember: 0.17 in precipitation 0.2 SepOctober: 1.92 in precipitation 1.9 OctNovember: 4.09 in precipitation 4.1 NovDecember: 8.30 in precipitation 8.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Angwin Pacific Union College, CA (within 1 mile); precipitation: Angwin Pacific Union College, CA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

945769b
Deer Park, CA · 3 mi
945749b
Saint Helena, CA · 3 mi
945679a
Pope Valley, CA · 6 mi
945739b
Rutherford, CA · 9 mi
945159b
Calistoga, CA · 10 mi
945629b
Oakville, CA · 11 mi
954099b
Santa Rosa, CA · 11 mi
954529b
Kenwood, CA · 12 mi

California planting zones →

Questions about 94508

What planting zone is ZIP code 94508?

ZIP code 94508 (Angwin, 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 Angwin, CA?

The median last spring frost (32 °F) near 94508 is April 7; after April 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Angwin Pacific Union College station.

When is the first frost in Angwin, CA?

The median first fall frost near 94508 is December 5, giving a median frost-free growing season of 245 days.

When should I plant tomatoes in 94508?

Start tomato seeds indoors around Feb 10 – Feb 24 and set transplants outside around Apr 14 – Apr 28, one to three weeks after the median last frost.

How much rain and snow does 94508 get?

About 39.7 inches of precipitation a year (NOAA 1991–2020 normals, Angwin Pacific Union College station).

How hot do summers get in Angwin, CA?

The average high peaks at 85 °F in July, with about 27 days a year at 90 °F or more.

What kind of soil does 94508 have?

The USDA soil survey maps Aiken at the center of ZIP 94508: loam, well drained, pH about 5.8 (moderately acidic).

Did spring come early in Angwin, CA in 2026?

Spring leaf-out near 94508 came on Jan 20 in 2026, 12 days earlier than the 1991–2020 average (Feb 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Angwin, CA?

Intermediate onions: the longest day near 94508 is 14 h 52 min, so day-neutral types bulb best; long-day varieties may not bulb fully.