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

Planting zone for 95423 — Clearlake Oaks, CA

ZIP code 95423 (Clearlake Oaks, Lake County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is April 10 and the first fall frost November 6.

Where ZIP 95423 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.

Zone9a20 to 25 °F
Coldest night−6.7 to −3.9 °C
Last frostApr 10
First frostNov 6
2012 zone9b

Was 9b on the 2012 map — half a zone colder now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Clearlake Oaks, 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 Clearlake Oaks, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 10median — 50% chance of a later frost
Safe for tender plantsApril 30only 10% chance of frost after
First fall frostNovember 6median — 10% chance by Oct 24
Growing season209 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 14 and returns around November 21.

From the NOAA station Clearlake 4 Se, CA — 11 miles away, elevation 1,348 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 95423

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 27 – Mar 13
SpinachSow outdoors · Feb 27 – Mar 20
Broccoli, cabbageStart indoors · Jan 30 – Feb 13
Broccoli, cabbageTransplant · Mar 20 – Apr 3
Onion setsPlant outdoors · Mar 13 – Mar 27
PotatoesPlant outdoors · Mar 20 – Apr 3
LettuceSow outdoors · Mar 13 – Mar 27
Carrots, beetsSow outdoors · Mar 20 – Apr 3
TomatoesStart indoors · Feb 13 – Feb 27
TomatoesTransplant · Apr 17 – May 1
Peppers, eggplantStart indoors · Jan 30 – Feb 13
Peppers, eggplantTransplant · Apr 24 – May 8
BeansSow outdoors · Apr 17 – May 1
Sweet cornSow outdoors · Apr 17 – May 1
Cucumbers, squashSow outdoors · Apr 17 – May 1
Fall lettuce, spinachSow outdoors · Sep 11 – Sep 25
GarlicPlant cloves · Oct 23 – Nov 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Nov 6) 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 95423 came on Jan 25 — 10 days earlier than the 1991–2020 average (Feb 4).

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 Clearlake Oaks, CA

The soil mapped at the center of ZIP 95423 is Millsholm — loam, well drained.

TextureLoama good balance for most vegetables
pH6.5neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Millsholm-Bressa loams, 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 95423; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Clearlake Oaks, CA

Summer high91 °Faverage high, July
Winter low33 °Faverage low, January
Hot days66days a year at 90 °F or more
Freezing nights72nights a year at 32 °F or less
Growing degree days3,335base 50 °F — the season’s usable heat
Longest day14 h 55 mindaylight on June 21
Shortest day9 h 25 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation29.9 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 55 °F, low 33 °F 55°33° JanFebruary: average high 58 °F, low 34 °F 58°34° FebMarch: average high 62 °F, low 35 °F 62°35° MarApril: average high 66 °F, low 39 °F 66°39° AprMay: average high 73 °F, low 45 °F 73°45° MayJune: average high 83 °F, low 52 °F 83°52° JunJuly: average high 91 °F, low 56 °F 91°56° JulAugust: average high 91 °F, low 54 °F 91°54° AugSeptember: average high 85 °F, low 50 °F 85°50° SepOctober: average high 75 °F, low 43 °F 75°43° OctNovember: average high 63 °F, low 36 °F 63°36° NovDecember: average high 55 °F, low 33 °F 55°33° Dec

Precipitation by month inches

0″2″4″6″January: 6.19 in precipitation, 0.2 in snowfall 6.2 JanFebruary: 6.15 in precipitation, 0.1 in snowfall 6.2 FebMarch: 3.99 in precipitation, 0.1 in snowfall 4.0 MarApril: 1.99 in precipitation 2.0 AprMay: 1.16 in precipitation 1.2 MayJune: 0.23 in precipitation 0.2 JunJuly: 0.01 in precipitation 0.0 JulAugust: 0.09 in precipitation 0.1 AugSeptember: 0.17 in precipitation 0.2 SepOctober: 0.91 in precipitation 0.9 OctNovember: 2.89 in precipitation 2.9 NovDecember: 6.08 in precipitation 6.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Clearlake 4 Se, CA (11 mi away); precipitation: Clearlake 4 Se, CA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

954229a
Clearlake, CA · 6 mi
954439b
Glenhaven, CA · 6 mi
954249a
Clearlake Park, CA · 7 mi
954589a
Lucerne, CA · 8 mi
954579a
Lower Lake, CA · 11 mi
954648b
Nice, CA · 12 mi
954519b
Kelseyville, CA · 13 mi
954358b
Finley, CA · 14 mi

California planting zones →

Questions about 95423

What planting zone is ZIP code 95423?

ZIP code 95423 (Clearlake Oaks, CA) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Clearlake Oaks, CA?

The median last spring frost (32 °F) near 95423 is April 10; after April 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Clearlake 4 Se station.

When is the first frost in Clearlake Oaks, CA?

The median first fall frost near 95423 is November 6, giving a median frost-free growing season of 209 days.

When should I plant tomatoes in 95423?

Start tomato seeds indoors around Feb 13 – Feb 27 and set transplants outside around Apr 17 – May 1, one to three weeks after the median last frost.

How much rain and snow does 95423 get?

About 29.9 inches of precipitation a year (NOAA 1991–2020 normals, Clearlake 4 Se station).

How hot do summers get in Clearlake Oaks, CA?

The average high peaks at 91 °F in July, with about 66 days a year at 90 °F or more.

What kind of soil does 95423 have?

The USDA soil survey maps Millsholm at the center of ZIP 95423: loam, well drained, pH about 6.5 (neutral).

Did spring come early in Clearlake Oaks, CA in 2026?

Spring leaf-out near 95423 came on Jan 25 in 2026, 10 days earlier than the 1991–2020 average (Feb 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Clearlake Oaks, CA?

Intermediate onions: the longest day near 95423 is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 95423 change?

Yes. The 2012 USDA map put 95423 in zone 9b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.