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

Planting zone for 99641 — Nunapitchuk, AK

ZIP code 99641 (Nunapitchuk, Bethel Census Area County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 21 and the first fall frost September 22.

Where ZIP 99641 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.

Zone4a−30 to −25 °F
Coldest night−34.4 to −31.7 °C
Last frostMay 21
First frostSep 22
2012 zone3b

Was 3b 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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Nunapitchuk, 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 Nunapitchuk, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 21median — 50% chance of a later frost
Safe for tender plantsJune 2only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 7
Growing season122 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 11 and returns around October 1.

From the NOAA station Bethel Airport, AK — 22 miles away, elevation 102 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 99641

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 9 – Apr 23
SpinachSow outdoors · Apr 9 – Apr 30
Broccoli, cabbageStart indoors · Mar 12 – Mar 26
Broccoli, cabbageTransplant · Apr 30 – May 14
Onion setsPlant outdoors · Apr 23 – May 7
PotatoesPlant outdoors · Apr 30 – May 14
LettuceSow outdoors · Apr 23 – May 7
Carrots, beetsSow outdoors · Apr 30 – May 14
TomatoesStart indoors · Mar 26 – Apr 9
TomatoesTransplant · May 28 – Jun 11
Peppers, eggplantStart indoors · Mar 12 – Mar 26
Peppers, eggplantTransplant · Jun 4 – Jun 18
BeansSow outdoors · May 28 – Jun 11
Sweet cornSow outdoors · May 28 – Jun 11
Cucumbers, squashSow outdoors · May 28 – Jun 11
Fall lettuce, spinachSow outdoors · Jul 28 – Aug 11
GarlicPlant cloves · Sep 8 – Oct 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 21) and first fall frost (Sep 22) 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.

Soil in Nunapitchuk, AK

The soil mapped at the center of ZIP 99641 is Oscarville — mucky peat, very poorly drained.

TextureMucky peattop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter75%high
Hydrologic groupB/Dmoderate when drained; wet otherwise

Map unit: Oscarville-Water complex, 0 to 3 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 99641; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Nunapitchuk, AK

Summer high64 °Faverage high, July
Winter low1 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights214nights a year at 32 °F or less
Growing degree days501base 50 °F — the season’s usable heat
Longest day19 h 13 mindaylight on June 21
Shortest day5 h 34 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation19.7 inper year, rain and melted snow
Snowfall64 inper year; 153 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°32 °FJanuary: average high 13 °F, low 1 °F 13°1° JanFebruary: average high 20 °F, low 7 °F 20°7° FebMarch: average high 22 °F, low 7 °F 22°7° MarApril: average high 37 °F, low 21 °F 37°21° AprMay: average high 52 °F, low 34 °F 52°34° MayJune: average high 62 °F, low 45 °F 62°45° JunJuly: average high 64 °F, low 49 °F 64°49° JulAugust: average high 61 °F, low 47 °F 61°47° AugSeptember: average high 53 °F, low 39 °F 53°39° SepOctober: average high 38 °F, low 26 °F 38°26° OctNovember: average high 24 °F, low 13 °F 24°13° NovDecember: average high 16 °F, low 4 °F 16°4° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″January: 0.77 in precipitation, 9.4 in snowfall 0.8❄9 JanFebruary: 0.88 in precipitation, 8.1 in snowfall 0.9❄8 FebMarch: 0.74 in precipitation, 8.8 in snowfall 0.7❄9 MarApril: 0.79 in precipitation, 6 in snowfall 0.8❄6 AprMay: 1.21 in precipitation, 1.9 in snowfall 1.2❄2 MayJune: 1.77 in precipitation 1.8 JunJuly: 2.57 in precipitation 2.6 JulAugust: 3.36 in precipitation 3.4 AugSeptember: 2.89 in precipitation, 0.5 in snowfall 2.9❄1 SepOctober: 1.84 in precipitation, 3.9 in snowfall 1.8❄4 OctNovember: 1.80 in precipitation, 13.2 in snowfall 1.8❄13 NovDecember: 1.06 in precipitation, 12.2 in snowfall 1.1❄12 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Bethel Airport, AK (22 mi away); precipitation: Bethel Airport, AK (22 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

996094a
Kasigluk, AK · 3 mi
996344a
Napakiak, AK · 20 mi
995594a
Bethel, AK · 21 mi
996214a
Kwethluk, AK · 35 mi
995513b
Akiachak, AK · 36 mi
996804a
Tuntutuliak, AK · 38 mi
995784a
Eek, AK · 48 mi
995454a
Kongiganak, AK · 65 mi

Alaska planting zones →

Questions about 99641

What planting zone is ZIP code 99641?

ZIP code 99641 (Nunapitchuk, AK) is in USDA hardiness zone 4a on the 2023 map: the coldest night of an average winter reaches −30 to −25 °F (−34.4 to −31.7 °C).

When is the last frost in Nunapitchuk, AK?

The median last spring frost (32 °F) near 99641 is May 21; after June 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bethel Airport station.

When is the first frost in Nunapitchuk, AK?

The median first fall frost near 99641 is September 22, giving a median frost-free growing season of 122 days.

When should I plant tomatoes in 99641?

Start tomato seeds indoors around Mar 26 – Apr 9 and set transplants outside around May 28 – Jun 11, one to three weeks after the median last frost.

How much rain and snow does 99641 get?

About 19.7 inches of precipitation a year and 64 inches of snowfall (NOAA 1991–2020 normals, Bethel Airport station).

How hot do summers get in Nunapitchuk, AK?

The average high peaks at 64 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99641 have?

The USDA soil survey maps Oscarville at the center of ZIP 99641: mucky peat, very poorly drained, pH about 5.0 (strongly acidic).

What kind of onions grow in Nunapitchuk, AK?

Long-day onions: the longest day near 99641 is 19 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99641 change?

Yes. The 2012 USDA map put 99641 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.