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

Planting zone for 95589 — Whitethorn, CA

ZIP code 95589 (Whitethorn, Humboldt County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is March 10 and the first fall frost December 1.

Where ZIP 95589 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 10
First frostDec 1
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 Whitethorn, 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 Whitethorn, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 10median — 50% chance of a later frost
Safe for tender plantsApril 13only 10% chance of frost after
First fall frostDecember 1median — 10% chance by Nov 7
Growing season271 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 15 and returns around December 26.

From the NOAA station Richardson Gr Sp, CA — 10 miles away, elevation 502 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 95589

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 27 – Feb 10
SpinachSow outdoors · Jan 27 – Feb 17
Broccoli, cabbageStart indoors · Dec 30 – Jan 13
Broccoli, cabbageTransplant · Feb 17 – Mar 3
Onion setsPlant outdoors · Feb 10 – Feb 24
PotatoesPlant outdoors · Feb 17 – Mar 3
LettuceSow outdoors · Feb 10 – Feb 24
Carrots, beetsSow outdoors · Feb 17 – Mar 3
TomatoesStart indoors · Jan 13 – Jan 27
TomatoesTransplant · Mar 17 – Mar 31
Peppers, eggplantStart indoors · Dec 30 – Jan 13
Peppers, eggplantTransplant · Mar 24 – Apr 7
BeansSow outdoors · Mar 17 – Mar 31
Sweet cornSow outdoors · Mar 17 – Mar 31
Cucumbers, squashSow outdoors · Mar 17 – Mar 31
Fall lettuce, spinachSow outdoors · Oct 6 – Oct 20
GarlicPlant cloves · Nov 17 – Dec 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 10) and first fall frost (Dec 1) 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 95589 came on Feb 2 — about the same time as the 1991–2020 average (Feb 3).

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 Whitethorn, CA

The soil mapped at the center of ZIP 95589 is Sproulish — 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 groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Sproulish-Canoecreek-Redwohly 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 95589; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Whitethorn, CA

Summer high70 °Faverage high, September
Winter low47 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights1nights a year at 32 °F or less
Growing degree days2,616base 50 °F — the season’s usable heat
Longest day15 h 01 mindaylight on June 21
Shortest day9 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation88.2 inper year, rain and melted snow

Average high and low, by month

40°50°60°70°80°January: average high 58 °F, low 47 °F 58°47° JanFebruary: average high 59 °F, low 47 °F 59°47° FebMarch: average high 61 °F, low 47 °F 61°47° MarApril: average high 62 °F, low 47 °F 62°47° AprMay: average high 65 °F, low 49 °F 65°49° MayJune: average high 68 °F, low 52 °F 68°52° JunJuly: average high 68 °F, low 53 °F 68°53° JulAugust: average high 68 °F, low 54 °F 68°54° AugSeptember: average high 70 °F, low 54 °F 70°54° SepOctober: average high 69 °F, low 52 °F 69°52° OctNovember: average high 62 °F, low 49 °F 62°49° NovDecember: average high 59 °F, low 47 °F 59°47° Dec

Precipitation by month inches

0″2″4″6″8″10″12″14″16″18″January: 17.56 in precipitation 17.6 JanFebruary: 14.23 in precipitation 14.2 FebMarch: 13.63 in precipitation 13.6 MarApril: 10.14 in precipitation 10.1 AprMay: 3.56 in precipitation 3.6 MayJune: 0.57 in precipitation 0.6 JunJuly: 0.13 in precipitation 0.1 JulAugust: 0.18 in precipitation 0.2 AugSeptember: 0.49 in precipitation 0.5 SepOctober: 2.88 in precipitation 2.9 OctNovember: 10.34 in precipitation 10.3 NovDecember: 14.50 in precipitation 14.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Shelter Cove Aviation, CA (6 mi away); precipitation: Whitethorn 1.7 Nnw, CA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

955609b
Redway, CA · 9 mi
955429a
Garberville, CA · 12 mi
955539b
Miranda, CA · 13 mi
955879a
Piercy, CA · 13 mi
955459b
Honeydew, CA · 15 mi
955599a
Phillipsville, CA · 15 mi
955549b
Myers Flat, CA · 19 mi
955719b
Weott, CA · 21 mi

California planting zones →

Questions about 95589

What planting zone is ZIP code 95589?

ZIP code 95589 (Whitethorn, 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 Whitethorn, CA?

The median last spring frost (32 °F) near 95589 is March 10; after April 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Richardson Gr Sp station.

When is the first frost in Whitethorn, CA?

The median first fall frost near 95589 is December 1, giving a median frost-free growing season of 271 days.

When should I plant tomatoes in 95589?

Start tomato seeds indoors around Jan 13 – Jan 27 and set transplants outside around Mar 17 – Mar 31, one to three weeks after the median last frost.

How much rain and snow does 95589 get?

About 88.2 inches of precipitation a year (NOAA 1991–2020 normals, Whitethorn 1.7 Nnw station).

How hot do summers get in Whitethorn, CA?

The average high peaks at 70 °F in September, with about 1 days a year at 90 °F or more.

What kind of soil does 95589 have?

The USDA soil survey maps Sproulish at the center of ZIP 95589: slightly decomposed plant material, well drained, pH about 6.0 (slightly acidic).

Did spring come early in Whitethorn, CA in 2026?

Spring leaf-out near 95589 came on Feb 2 in 2026, about the same as the 1991–2020 average (Feb 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Whitethorn, CA?

Long-day onions: the longest day near 95589 is 15 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).