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

Planting zone for 99651 — Platinum, AK

ZIP code 99651 (Platinum, Bethel Census Area County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F.

Where ZIP 99651 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostrare
First frostrare
2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Platinum, 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 Platinum, 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 4b in Alaska

260 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 11

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 °FPacific silver fir165 ft · blooms late spring · low shade tolerance · to −28 °Fpaper birch70 ft · blooms mid spring · high shade tolerance · to −62 °Fquaking aspen65 ft · blooms mid spring · high shade tolerance · to −70 °F

Shrubs 44

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FBarclay's willow15 ft · high shade tolerance · to −43 °Fblack crowberry1 ft · blooms mid summer · high shade tolerance · to −43 °Fblack hawthorn15 ft · blooms mid spring · medium shade tolerance · to −47 °Fbog blueberry2 ft · blooms early summer · medium shade tolerance · to −38 °F

Wildflowers & perennials 112

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine aster0.3 ft · blooms early summer · medium shade tolerance · to −28 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °F

Grasses 84

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Farctic bluegrass2 ft · high shade tolerance · to −62 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °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 Platinum, AK.

Soil in Platinum, AK

The soil mapped at the center of ZIP 99651 is E37-maritime tall scrub-gravelly colluvial slopes — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Ahklun Mountains-Northwest Maritime Upland-Rounded Mountains.

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 99651; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Platinum, AK

Longest day18 h 29 mindaylight on June 21
Shortest day6 h 11 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

4 of the 7 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

995894b
Goodnews Bay, AK · 21 mi
996784b
Togiak, AK · 50 mi
996554b
Quinhagak, AK · 55 mi
995454a
Kongiganak, AK · 80 mi
996224a
Kwigillingok, AK · 81 mi
995784a
Eek, AK · 88 mi
996804a
Tuntutuliak, AK · 101 mi

Alaska planting zones →

Questions about 99651

What planting zone is ZIP code 99651?

ZIP code 99651 (Platinum, AK) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

What kind of soil does 99651 have?

The USDA soil survey maps E37-maritime tall scrub-gravelly colluvial slopes at the center of ZIP 99651: slightly decomposed plant material, well drained.

What kind of onions grow in Platinum, AK?

Long-day onions: the longest day near 99651 is 18 h 29 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).