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

Planting zone for 96728 — Honomu, HI

ZIP code 96728 (Honomu, Hawaii County) is in USDA zone 12b: the coldest winter night averages 55 to 60 °F. The median last spring frost is April 12 and the first fall frost December 1.

Where ZIP 96728 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.

Zone12b55 to 60 °F

Coldest night12.8 to 15.6 °C

Last frostApr 12

First frostDec 1

2012 zone12b

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 12b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Honomu, HI…

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 Honomu, HI

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 12median — 50% chance of a later frost

Safe for tender plantsMay 18only 10% chance of frost after

First fall frostDecember 1median — 10% chance by Nov 9

Growing season235 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 13 and returns around January 22.

From the NOAA station Mauna Loa 5 Nne, HI — 37 miles away, elevation 11,178 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 96728

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 1 – Mar 15

SpinachSow outdoors · Mar 1 – Mar 22

Broccoli, cabbageStart indoors · Feb 1 – Feb 15

Broccoli, cabbageTransplant · Mar 22 – Apr 5

Onion setsPlant outdoors · Mar 15 – Mar 29

PotatoesPlant outdoors · Mar 22 – Apr 5

LettuceSow outdoors · Mar 15 – Mar 29

Carrots, beetsSow outdoors · Mar 22 – Apr 5

TomatoesStart indoors · Feb 15 – Mar 1

TomatoesTransplant · Apr 19 – May 3

Peppers, eggplantStart indoors · Feb 1 – Feb 15

Peppers, eggplantTransplant · Apr 26 – May 10

BeansSow outdoors · Apr 19 – May 3

Sweet cornSow outdoors · Apr 19 – May 3

Cucumbers, squashSow outdoors · Apr 19 – May 3

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 (Apr 12) 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.

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 Honomu, HI.

Soil in Honomu, HI

The soil mapped at the center of ZIP 96728 is Hilo — hydrous silty clay loam, well drained.

TextureHydrous silty clay loamholds water and nutrients; slow to drain and warm up

pH5.8moderately acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter9%high

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Hilo hydrous silty clay loam, 10 to 20 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 96728; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Honomu, HI

Summer high81 °Faverage high, August

Winter low61 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights0nights a year at 32 °F or less

Growing degree days7,808base 50 °F — the season’s usable heat

Longest day13 h 20 mindaylight on June 21

Shortest day10 h 56 mindaylight on December 21

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

Precipitation216.7 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: Kihalani 132.5, HI (11 mi away); precipitation: Kahuna Falls 138.2, HI (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.

Laupahoehoe, HI · 12 mi

9677411a

Ookala, HI · 14 mi

Hawaii planting zones →

Questions about 96728

What planting zone is ZIP code 96728?

ZIP code 96728 (Honomu, HI) is in USDA hardiness zone 12b on the 2023 map: the coldest night of an average winter reaches 55 to 60 °F (12.8 to 15.6 °C).

When is the last frost in Honomu, HI?

The median last spring frost (32 °F) near 96728 is April 12; after May 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mauna Loa 5 Nne station.

When is the first frost in Honomu, HI?

The median first fall frost near 96728 is December 1, giving a median frost-free growing season of 235 days.

When should I plant tomatoes in 96728?

Start tomato seeds indoors around Feb 15 – Mar 1 and set transplants outside around Apr 19 – May 3, one to three weeks after the median last frost.

How much rain and snow does 96728 get?

About 216.7 inches of precipitation a year (NOAA 1991–2020 normals, Kahuna Falls 138.2 station).

How hot do summers get in Honomu, HI?

The average high peaks at 81 °F in August, with about 0 days a year at 90 °F or more.

What kind of soil does 96728 have?

The USDA soil survey maps Hilo at the center of ZIP 96728: hydrous silty clay loam, well drained, pH about 5.8 (moderately acidic).

What kind of onions grow in Honomu, HI?

Short-day onions: the longest day near 96728 is 13 h 20 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.