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

Planting zone for 99770 — Selawik, AK

ZIP code 99770 (Selawik, Northwest Arctic County) is in USDA zone 2a: the coldest winter night averages −50 to −45 °F. The median last spring frost is June 5 and the first fall frost September 24.

Where ZIP 99770 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.

Zone2a−50 to −45 °F

Coldest night−45.6 to −42.8 °C

Last frostJun 5

First frostSep 24

2012 zone2a

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 2a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Selawik, 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 Selawik, AK

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 5median — 50% chance of a later frost

Safe for tender plantsJune 17only 10% chance of frost after

First fall frostSeptember 24median — 10% chance by Sep 7

Growing season110 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 27 and returns around October 3.

From the NOAA station Kotzebue Ralph Wein Airport, AK — 71 miles away, elevation 30 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 99770

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 24 – May 8

SpinachSow outdoors · Apr 24 – May 15

Broccoli, cabbageStart indoors · Mar 27 – Apr 10

Broccoli, cabbageTransplant · May 15 – May 29

Onion setsPlant outdoors · May 8 – May 22

PotatoesPlant outdoors · May 15 – May 29

LettuceSow outdoors · May 8 – May 22

Carrots, beetsSow outdoors · May 15 – May 29

TomatoesStart indoors · Apr 10 – Apr 24

TomatoesTransplant · Jun 12 – Jun 26

Peppers, eggplantStart indoors · Mar 27 – Apr 10

Peppers, eggplantTransplant · Jun 19 – Jul 3

BeansSow outdoors · Jun 12 – Jun 26

Sweet cornSow outdoors · Jun 12 – Jun 26

Cucumbers, squashSow outdoors · Jun 12 – Jun 26

Fall lettuce, spinachSow outdoors · Jul 30 – Aug 13

GarlicPlant cloves · Sep 10 – Oct 15

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 5) and first fall frost (Sep 24) 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 Selawik, AK

The soil mapped at the center of ZIP 99770 is E42-Arctic scrub-silty frozen mid coastal plains — peat, very poorly drained.

TexturePeattop layer

pH6.2slightly acidic; most vegetables like 6.0–7.0

DrainageVery poorly drainedconsider raised beds

Organic matter75%high

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Northern Seward Peninsula-Selawik Lowlands-Arctic Lowland-Coastal Plains, Low.

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 99770; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Selawik, AK

Summer high60 °Faverage high, July

Winter low−8 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights236nights a year at 32 °F or less

Growing degree days372base 50 °F — the season’s usable heat

Longest day24 h 00 mindaylight on June 21

Shortest day2 h 06 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Average high and low, by month

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kotzebue Ralph Wein Airport, AK (71 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Alaska planting zones →

Questions about 99770

What planting zone is ZIP code 99770?

ZIP code 99770 (Selawik, AK) is in USDA hardiness zone 2a on the 2023 map: the coldest night of an average winter reaches −50 to −45 °F (−45.6 to −42.8 °C).

When is the last frost in Selawik, AK?

The median last spring frost (32 °F) near 99770 is June 5; after June 17 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kotzebue Ralph Wein Airport station.

When is the first frost in Selawik, AK?

The median first fall frost near 99770 is September 24, giving a median frost-free growing season of 110 days.

When should I plant tomatoes in 99770?

Start tomato seeds indoors around Apr 10 – Apr 24 and set transplants outside around Jun 12 – Jun 26, one to three weeks after the median last frost.

How hot do summers get in Selawik, AK?

The average high peaks at 60 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99770 have?

The USDA soil survey maps E42-Arctic scrub-silty frozen mid coastal plains at the center of ZIP 99770: peat, very poorly drained, pH about 6.2 (slightly acidic).

What kind of onions grow in Selawik, AK?

Long-day onions: the longest day near 99770 is 24 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).