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

Planting zone for 95558 — Petrolia, CA

ZIP code 95558 (Petrolia, Humboldt County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is February 1 and the first fall frost December 19.

Where ZIP 95558 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 frostFeb 1
First frostDec 19
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 Petrolia, 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 Petrolia, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 1median — 50% chance of a later frost
Safe for tender plantsMarch 8only 10% chance of frost after
First fall frostDecember 19median — 10% chance by Nov 19
Growing season328 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 3 and returns around December 31.

From the NOAA station Scotia, CA — 13 miles away, elevation 138 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 95558

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Dec 21 – Jan 4
SpinachSow outdoors · Dec 21 – Jan 11
Broccoli, cabbageStart indoors · Nov 23 – Dec 7
Broccoli, cabbageTransplant · Jan 11 – Jan 25
Onion setsPlant outdoors · Jan 4 – Jan 18
PotatoesPlant outdoors · Jan 11 – Jan 25
LettuceSow outdoors · Jan 4 – Jan 18
Carrots, beetsSow outdoors · Jan 11 – Jan 25
TomatoesStart indoors · Dec 7 – Dec 21
TomatoesTransplant · Feb 8 – Feb 22
Peppers, eggplantStart indoors · Nov 23 – Dec 7
Peppers, eggplantTransplant · Feb 15 – Mar 1
BeansSow outdoors · Feb 8 – Feb 22
Sweet cornSow outdoors · Feb 8 – Feb 22
Cucumbers, squashSow outdoors · Feb 8 – Feb 22
Fall lettuce, spinachSow outdoors · Oct 24 – Nov 7
GarlicPlant cloves · Dec 5 – Jan 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 1) and first fall frost (Dec 19) 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 95558 came on Jan 29 — 4 days earlier than the 1991–2020 average (Feb 2).

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 Petrolia, CA

The soil mapped at the center of ZIP 95558 is Crazycoyote — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Crazycoyote-Sproulish-Canoecreek complex, 50 to 75 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 95558; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Petrolia, CA

Summer high73 °Faverage high, September
Winter low42 °Faverage low, December
Hot days2days a year at 90 °F or more
Freezing nights6nights a year at 32 °F or less
Growing degree days2,346base 50 °F — the season’s usable heat
Longest day15 h 03 mindaylight on June 21
Shortest day9 h 17 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation68.8 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°32 °FJanuary: average high 57 °F, low 43 °F 57°43° JanFebruary: average high 58 °F, low 43 °F 58°43° FebMarch: average high 59 °F, low 44 °F 59°44° MarApril: average high 62 °F, low 45 °F 62°45° AprMay: average high 64 °F, low 49 °F 64°49° MayJune: average high 67 °F, low 51 °F 67°51° JunJuly: average high 70 °F, low 54 °F 70°54° JulAugust: average high 72 °F, low 54 °F 72°54° AugSeptember: average high 73 °F, low 52 °F 73°52° SepOctober: average high 69 °F, low 48 °F 69°48° OctNovember: average high 61 °F, low 45 °F 61°45° NovDecember: average high 55 °F, low 42 °F 55°42° Dec

Precipitation by month inches

0″2″4″6″8″10″12″January: 12.63 in precipitation 12.6 JanFebruary: 12.26 in precipitation 12.3 FebMarch: 10.59 in precipitation 10.6 MarApril: 5.10 in precipitation 5.1 AprMay: 2.24 in precipitation 2.2 MayJune: 0.89 in precipitation 0.9 JunJuly: 0.16 in precipitation 0.2 JulAugust: 0.12 in precipitation 0.1 AugSeptember: 0.82 in precipitation 0.8 SepOctober: 3.47 in precipitation 3.5 OctNovember: 8.93 in precipitation 8.9 NovDecember: 11.63 in precipitation 11.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Scotia, CA (13 mi away); precipitation: Petrolia 0.6 Sse, CA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

955459b
Honeydew, CA · 11 mi
955629b
Rio Dell, CA · 11 mi
955369b
Ferndale, CA · 12 mi
955659b
Scotia, CA · 15 mi
955409b
Fortuna, CA · 17 mi
955479b
Hydesville, CA · 19 mi
955519b
Loleta, CA · 23 mi
955379b
Fields Landing, CA · 27 mi

California planting zones →

Questions about 95558

What planting zone is ZIP code 95558?

ZIP code 95558 (Petrolia, 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 Petrolia, CA?

The median last spring frost (32 °F) near 95558 is February 1; after March 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Scotia station.

When is the first frost in Petrolia, CA?

The median first fall frost near 95558 is December 19, giving a median frost-free growing season of 328 days.

When should I plant tomatoes in 95558?

Start tomato seeds indoors around Dec 7 – Dec 21 and set transplants outside around Feb 8 – Feb 22, one to three weeks after the median last frost.

How much rain and snow does 95558 get?

About 68.8 inches of precipitation a year (NOAA 1991–2020 normals, Petrolia 0.6 Sse station).

How hot do summers get in Petrolia, CA?

The average high peaks at 73 °F in September, with about 2 days a year at 90 °F or more.

What kind of soil does 95558 have?

The USDA soil survey maps Crazycoyote at the center of ZIP 95558: slightly decomposed plant material, well drained, pH about 6.0 (slightly acidic).

Did spring come early in Petrolia, CA in 2026?

Spring leaf-out near 95558 came on Jan 29 in 2026, 4 days earlier than the 1991–2020 average (Feb 2), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Petrolia, CA?

Long-day onions: the longest day near 95558 is 15 h 03 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).