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

Planting zone for 99753 — Koyuk, AK

ZIP code 99753 (Koyuk, Nome (CA) County) is in USDA zone 3b: the coldest winter night averages −35 to −30 °F. The median last spring frost is May 25 and the first fall frost September 3.

Where ZIP 99753 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.

Zone3b−35 to −30 °F
Coldest night−37.2 to −34.4 °C
Last frostMay 25
First frostSep 3
2012 zone3a

Was 3a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 3b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Koyuk, 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 in Koyuk, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 25median — 50% chance of a later frost
Safe for tender plantsJune 11only 10% chance of frost after
First fall frostSeptember 3median — 10% chance by Aug 18
Growing season101 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 12 and returns around September 17.

From the NOAA station Kaltag Airport, AK — 82 miles away, elevation 180 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 99753

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 13 – Apr 27
SpinachSow outdoors · Apr 13 – May 4
Broccoli, cabbageStart indoors · Mar 16 – Mar 30
Broccoli, cabbageTransplant · May 4 – May 18
Onion setsPlant outdoors · Apr 27 – May 11
PotatoesPlant outdoors · May 4 – May 18
LettuceSow outdoors · Apr 27 – May 11
Carrots, beetsSow outdoors · May 4 – May 18
TomatoesStart indoors · Mar 30 – Apr 13
TomatoesTransplant · Jun 1 – Jun 15
Peppers, eggplantStart indoors · Mar 16 – Mar 30
Peppers, eggplantTransplant · Jun 8 – Jun 22
BeansSow outdoors · Jun 1 – Jun 15
Sweet cornSow outdoors · Jun 1 – Jun 15
Cucumbers, squashSow outdoors · Jun 1 – Jun 15
Fall lettuce, spinachSow outdoors · Jul 9 – Jul 23
GarlicPlant cloves · Aug 20 – Sep 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 25) and first fall frost (Sep 3) 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 3b in Alaska

172 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −35 °F or colder — the bottom of zone 3b. Each links to its USDA PLANTS profile.

Trees 8

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 °Fsubalpine fir90 ft · blooms late spring · low shade tolerance · to −51 °F

Shrubs 32

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °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 °Fchokecherry25 ft · blooms mid spring · high shade tolerance · to −43 °F

Wildflowers & perennials 64

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °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 speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °FAmerican vetch1.3 ft · blooms late spring · high shade tolerance · to −38 °F

Grasses 61

alpine 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 °Fbearded fescue1.2 ft · blooms late spring · low shade tolerance · to −38 °FBebb's sedge3 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 Koyuk, AK.

Soil in Koyuk, AK

The soil mapped at the center of ZIP 99753 is E40-maritime tussock-scrub-silty frozen high plains — peat, very poorly drained.

TexturePeattop layer
pH3.9strongly acidic; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter80%high
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Nulato Hills-Southern Seward Peninsula Highlands-Maritime Lowland-Coastal Plains.

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 99753; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Koyuk, AK

Summer high69 °Faverage high, June
Winter low−12 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights234nights a year at 32 °F or less
Growing degree days747base 50 °F — the season’s usable heat
Longest day21 h 58 mindaylight on June 21
Shortest day3 h 37 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation14 inper year, rain and melted snow

Average high and low, by month

−20°−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 4 °F, low -12 °F 4°−12° JanFebruary: average high 14 °F, low -6 °F 14°−6° FebMarch: average high 21 °F, low -2 °F 21°−2° MarApril: average high 38 °F, low 17 °F 38°17° AprMay: average high 56 °F, low 34 °F 56°34° MayJune: average high 69 °F, low 46 °F 69°46° JunJuly: average high 69 °F, low 49 °F 69°49° JulAugust: average high 64 °F, low 45 °F 64°45° AugSeptember: average high 53 °F, low 36 °F 53°36° SepOctober: average high 35 °F, low 21 °F 35°21° OctNovember: average high 17 °F, low 2 °F 17°2° NovDecember: average high 8 °F, low -8 °F 8°−8° Dec

Precipitation by month inches

0″1″2″3″January: 0.76 in precipitation 0.8 JanFebruary: 0.93 in precipitation 0.9 FebMarch: 0.75 in precipitation 0.8 MarApril: 0.65 in precipitation 0.7 AprMay: 0.61 in precipitation 0.6 MayJune: 0.85 in precipitation 0.8 JunJuly: 1.71 in precipitation 1.7 JulAugust: 2.34 in precipitation 2.3 AugSeptember: 1.74 in precipitation 1.7 SepOctober: 1.66 in precipitation 1.7 OctNovember: 1.06 in precipitation 1.1 NovDecember: 0.93 in precipitation 0.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kaltag Airport, AK (82 mi away); precipitation: Pargon Creek, AK (58 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

1 of the 5 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

997713b
Shaktoolik, AK · 40 mi
996843b
Unalakleet, AK · 66 mi
997272b
Buckland, AK · 72 mi
996593b
Saint Michael, AK · 107 mi
996713b
Stebbins, AK · 107 mi

Alaska planting zones →

Questions about 99753

What planting zone is ZIP code 99753?

ZIP code 99753 (Koyuk, AK) is in USDA hardiness zone 3b on the 2023 map: the coldest night of an average winter reaches −35 to −30 °F (−37.2 to −34.4 °C).

When is the last frost in Koyuk, AK?

The median last spring frost (32 °F) near 99753 is May 25; after June 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kaltag Airport station.

When is the first frost in Koyuk, AK?

The median first fall frost near 99753 is September 3, giving a median frost-free growing season of 101 days.

When should I plant tomatoes in 99753?

Start tomato seeds indoors around Mar 30 – Apr 13 and set transplants outside around Jun 1 – Jun 15, one to three weeks after the median last frost.

How much rain and snow does 99753 get?

About 14 inches of precipitation a year (NOAA 1991–2020 normals, Pargon Creek station).

How hot do summers get in Koyuk, AK?

The average high peaks at 69 °F in June, with about 0 days a year at 90 °F or more.

What kind of soil does 99753 have?

The USDA soil survey maps E40-maritime tussock-scrub-silty frozen high plains at the center of ZIP 99753: peat, very poorly drained, pH about 3.9 (strongly acidic).

What kind of onions grow in Koyuk, AK?

Long-day onions: the longest day near 99753 is 21 h 58 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99753 change?

Yes. The 2012 USDA map put 99753 in zone 3a; the 2023 map puts it in zone 3b. The newer map uses 1991–2020 data and more weather stations.