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

Planting zone for 99751 — Kobuk, AK

ZIP code 99751 (Kobuk, Northwest Arctic County) is in USDA zone 1b: the coldest winter night averages −55 to −50 °F.

Where ZIP 99751 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.

Zone1b−55 to −50 °F
Coldest night−48.3 to −45.6 °C
Last frostrare
First frostrare
2012 zone1b

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 1b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Kobuk, AK…

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

No NOAA station with frost records lies within 90 miles of Kobuk, AK, so we don't show frost dates here rather than guess. Your local extension office can give you a date.

Native plants for zone 1b in Alaska

37 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −55 °F or colder — the bottom of zone 1b. Each links to its USDA PLANTS profile.

Trees 7

balsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack spruce65 ft · blooms late spring · low shade tolerance · to −79 °Flodgepole pine99 ft · blooms mid summer · high shade tolerance · to −70 °Fpaper birch70 ft · blooms mid spring · high shade tolerance · to −62 °Fquaking aspen65 ft · blooms mid spring · high shade tolerance · to −70 °Ftamarack80 ft · blooms mid spring · high shade tolerance · to −79 °F

Shrubs 15

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °Fhalberd willow3 ft · blooms early summer · to −62 °FLapland rosebay3 ft · blooms late spring · low shade tolerance · to −62 °Flingonberry0.5 ft · blooms summer · high shade tolerance · to −62 °Fmarsh Labrador tea0.5 ft · blooms summer · to −62 °Fnetleaf willow0.2 ft · blooms early summer · to −62 °F

Wildflowers & perennials 11

alpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °Farctic dock1 ft · blooms summer · high shade tolerance · to −62 °Farctic lupine2 ft · blooms spring · medium shade tolerance · to −62 °Farctic raspberry1 ft · blooms summer · high shade tolerance · to −62 °Feightpetal mountain-avens0.3 ft · blooms late spring · medium shade tolerance · to −62 °Fhigh northern buttercup1 ft · blooms summer · high shade tolerance · to −62 °F

Grasses 2

arctic bluegrass2 ft · high shade tolerance · to −62 °Flivid sedge1 ft · blooms early summer · high shade tolerance · to −62 °F

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 Kobuk, AK.

Soil in Kobuk, AK

The soil mapped at the center of ZIP 99751 is E33-Boreal taiga-loamy frozen terraces — peat, poorly drained.

TexturePeattop layer
DrainagePoorly drainedconsider raised beds
Organic matter75%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Upper Kobuk and Koyukuk Hills and Valleys-Boreal Lowland-Flood Plains and Terraces.

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 99751; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kobuk, AK

Longest day24 h 00 mindaylight on June 21
Shortest day1 h 39 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Daylight is calculated from latitude.

Nearby ZIP codes

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

997731b
Shungnak, AK · 7 mi
997862a
Ambler, AK · 29 mi
997462a
Huslia, AK · 86 mi

Alaska planting zones →

Questions about 99751

What planting zone is ZIP code 99751?

ZIP code 99751 (Kobuk, AK) is in USDA hardiness zone 1b on the 2023 map: the coldest night of an average winter reaches −55 to −50 °F (−48.3 to −45.6 °C).

What kind of soil does 99751 have?

The USDA soil survey maps E33-Boreal taiga-loamy frozen terraces at the center of ZIP 99751: peat, poorly drained.

What kind of onions grow in Kobuk, AK?

Long-day onions: the longest day near 99751 is 24 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).