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

Planting zone for 93255 — Onyx, CA

ZIP code 93255 (Onyx, Kern County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is April 5 and the first fall frost November 3.

Where ZIP 93255 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 5
First frostNov 3
2012 zone8b

Was 8b on the 2012 map — half a zone warmer 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 Onyx, 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 Onyx, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 5median — 50% chance of a later frost
Safe for tender plantsApril 21only 10% chance of frost after
First fall frostNovember 3median — 10% chance by Oct 18
Growing season212 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 6 and returns around November 17.

From the NOAA station S Lake Fs, CA — 15 miles away, elevation 2,654 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 93255

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 22 – Mar 8
SpinachSow outdoors · Feb 22 – Mar 15
Broccoli, cabbageStart indoors · Jan 25 – Feb 8
Broccoli, cabbageTransplant · Mar 15 – Mar 29
Onion setsPlant outdoors · Mar 8 – Mar 22
PotatoesPlant outdoors · Mar 15 – Mar 29
LettuceSow outdoors · Mar 8 – Mar 22
Carrots, beetsSow outdoors · Mar 15 – Mar 29
TomatoesStart indoors · Feb 8 – Feb 22
TomatoesTransplant · Apr 12 – Apr 26
Peppers, eggplantStart indoors · Jan 25 – Feb 8
Peppers, eggplantTransplant · Apr 19 – May 3
BeansSow outdoors · Apr 12 – Apr 26
Sweet cornSow outdoors · Apr 12 – Apr 26
Cucumbers, squashSow outdoors · Apr 12 – Apr 26
Fall lettuce, spinachSow outdoors · Sep 8 – Sep 22
GarlicPlant cloves · Oct 20 – Nov 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 5) and first fall frost (Nov 3) 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 93255 came on Feb 4 — 19 days earlier than the 1991–2020 average (Feb 23).

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 Onyx, CA

The soil mapped at the center of ZIP 93255 is Tollhouse — gravelly coarse sandy loam, somewhat excessively drained.

TextureGravelly coarse sandy loamdrains and warms fast; dries out and needs more feeding
pH6.5neutral; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Tollhouse-Rock outcrop complex, 10 to 30 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 93255; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Onyx, CA

Summer high98 °Faverage high, July
Winter low30 °Faverage low, January
Hot days114days a year at 90 °F or more
Freezing nights80nights a year at 32 °F or less
Growing degree days4,736base 50 °F — the season’s usable heat
Longest day14 h 35 mindaylight on June 21
Shortest day9 h 44 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation9.3 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 59 °F, low 30 °F 59°30° JanFebruary: average high 62 °F, low 34 °F 62°34° FebMarch: average high 67 °F, low 36 °F 67°36° MarApril: average high 73 °F, low 40 °F 73°40° AprMay: average high 82 °F, low 52 °F 82°52° MayJune: average high 92 °F, low 59 °F 92°59° JunJuly: average high 98 °F, low 65 °F 98°65° JulAugust: average high 98 °F, low 62 °F 98°62° AugSeptember: average high 91 °F, low 55 °F 91°55° SepOctober: average high 81 °F, low 43 °F 81°43° OctNovember: average high 69 °F, low 34 °F 69°34° NovDecember: average high 58 °F, low 30 °F 58°30° Dec

Precipitation by month inches

0″1″2″January: 1.83 in precipitation 1.8 JanFebruary: 1.79 in precipitation 1.8 FebMarch: 1.45 in precipitation 1.4 MarApril: 0.60 in precipitation 0.6 AprMay: 0.37 in precipitation 0.4 MayJune: 0.11 in precipitation 0.1 JunJuly: 0.17 in precipitation 0.2 JulAugust: 0.12 in precipitation 0.1 AugSeptember: 0.14 in precipitation 0.1 SepOctober: 0.54 in precipitation 0.5 OctNovember: 0.64 in precipitation 0.6 NovDecember: 1.55 in precipitation 1.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: S Lake Fs, CA (15 mi away); precipitation: Onyx 2.8 Ene, CA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

932839a
Weldon, CA · 12 mi
935278b
Inyokern, CA · 17 mi
932409a
Lake Isabella, CA · 20 mi
935428b
Little Lake, CA · 21 mi
932858b
Wofford Heights, CA · 23 mi
932058b
Bodfish, CA · 23 mi
932388b
Kernville, CA · 25 mi
935198b
Cantil, CA · 26 mi

California planting zones →

Questions about 93255

What planting zone is ZIP code 93255?

ZIP code 93255 (Onyx, 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 Onyx, CA?

The median last spring frost (32 °F) near 93255 is April 5; after April 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, S Lake Fs station.

When is the first frost in Onyx, CA?

The median first fall frost near 93255 is November 3, giving a median frost-free growing season of 212 days.

When should I plant tomatoes in 93255?

Start tomato seeds indoors around Feb 8 – Feb 22 and set transplants outside around Apr 12 – Apr 26, one to three weeks after the median last frost.

How much rain and snow does 93255 get?

About 9.3 inches of precipitation a year (NOAA 1991–2020 normals, Onyx 2.8 Ene station).

How hot do summers get in Onyx, CA?

The average high peaks at 98 °F in July, with about 114 days a year at 90 °F or more.

What kind of soil does 93255 have?

The USDA soil survey maps Tollhouse at the center of ZIP 93255: gravelly coarse sandy loam, somewhat excessively drained, pH about 6.5 (neutral).

Did spring come early in Onyx, CA in 2026?

Spring leaf-out near 93255 came on Feb 4 in 2026, 19 days earlier than the 1991–2020 average (Feb 23), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Onyx, CA?

Intermediate onions: the longest day near 93255 is 14 h 35 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 93255 change?

Yes. The 2012 USDA map put 93255 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.