Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for Kahului, HI

Kahului, HI is in USDA zone 12b across its 2 ZIP codes.

Kahului on the zone map

Outlined: its 1 ZIP code areas · 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.

Zone12b55 to 60 °F

ZIP codes2

Last frostrare

First frostrare

Growing seasonall year

12b 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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

Frost is rare or absent here: Kahului, HI is in zone 12b, where the coldest night of a typical winter stays above freezing. Cool-season vegetables grow best from fall through spring; summer heat, not frost, is the limit.

Native plants for zone 12b in Hawaii

37 plants native to Hawaii, recorded in Hawaii, and rated by the USDA to survive 55 °F or colder — the bottom of zone 12b. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Kahului, HI.

Soil in Kahului, HI

The soil mapped at the center of ZIP 96733 is Puuone — sand, somewhat excessively drained.

TextureSanddrains and warms fast; dries out and needs more feeding

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter0.3%low — add compost

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Puuone sand, 7 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 96733; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kahului, HI

Summer high90 °Faverage high, August

Winter low64 °Faverage low, January

Hot days39days a year at 90 °F or more

Freezing nights0nights a year at 32 °F or less

Growing degree days9,898base 50 °F — the season’s usable heat

Longest day13 h 24 mindaylight on June 21

Shortest day10 h 52 mindaylight on December 21

Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb

Precipitation33.5 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kahului Airport, HI (3 mi away); precipitation: Waiehu Camp 484, HI (3 mi away). Daylight is calculated from latitude.

ZIP codes in Kahului

Hawaii planting zones →

Questions about Kahului

What planting zone is Kahului, HI?

Kahului, HI is in USDA hardiness zone 12b on the 2023 map (12b: 55 to 60 °F).

What kind of onions grow in Kahului, HI?

Short-day onions: the longest day is 13 h 24 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

How much rain and snow does Kahului, HI get?

About 33.5 inches of precipitation a year (NOAA 1991–2020 normals).