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

Planting zone for 99691 — Nikolai, AK

ZIP code 99691 (Nikolai, Yukon-Koyukuk (CA) County) is in USDA zone 2b: the coldest winter night averages −45 to −40 °F. The median last spring frost is May 30 and the first fall frost September 5.

Where ZIP 99691 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.

Zone2b−45 to −40 °F

Coldest night−42.8 to −40 °C

Last frostMay 30

First frostSep 5

2012 zone1b

Was 1b on the 2012 map — a full zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 2b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Nikolai, 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 Nikolai, AK

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 30median — 50% chance of a later frost

Safe for tender plantsJune 15only 10% chance of frost after

First fall frostSeptember 5median — 10% chance by Aug 22

Growing season97 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 15 and returns around September 18.

From the NOAA station Farewell Lake, AK — 13 miles away, elevation 1,060 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 99691

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 18 – May 2

SpinachSow outdoors · Apr 18 – May 9

Broccoli, cabbageStart indoors · Mar 21 – Apr 4

Broccoli, cabbageTransplant · May 9 – May 23

Onion setsPlant outdoors · May 2 – May 16

PotatoesPlant outdoors · May 9 – May 23

LettuceSow outdoors · May 2 – May 16

Carrots, beetsSow outdoors · May 9 – May 23

TomatoesStart indoors · Apr 4 – Apr 18

TomatoesTransplant · Jun 6 – Jun 20

Peppers, eggplantStart indoors · Mar 21 – Apr 4

Peppers, eggplantTransplant · Jun 13 – Jun 27

BeansSow outdoors · Jun 6 – Jun 20

Sweet cornSow outdoors · Jun 6 – Jun 20

Cucumbers, squashSow outdoors · Jun 6 – Jun 20

Fall lettuce, spinachSow outdoors · Jul 11 – Jul 25

GarlicPlant cloves · Aug 22 – Sep 26

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 30) and first fall frost (Sep 5) 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 2b in Alaska

45 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −45 °F or colder — the bottom of zone 2b. Each links to its USDA PLANTS profile.

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 Nikolai, AK.

Soil in Nikolai, AK

The soil mapped at the center of ZIP 99691 is E28-boreal taiga-gravelly frozen till slopes — 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: Interior Alaska Mountains-Boreal Glaciated Plains and Hills.

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 99691; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Nikolai, AK

Summer high70 °Faverage high, July

Winter low−12 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights227nights a year at 32 °F or less

Growing degree days682base 50 °F — the season’s usable heat

Longest day20 h 09 mindaylight on June 21

Shortest day4 h 50 mindaylight on December 21

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

Precipitation15.9 inper year, rain and melted snow

Snowfall96 inper year; 197 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Farewell Lake, AK (13 mi away); precipitation: Puntilla, AK (52 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

996272b

Mc Grath, AK · 65 mi

997572b

Lake Minchumina, AK · 81 mi

Alaska planting zones →

Questions about 99691

What planting zone is ZIP code 99691?

ZIP code 99691 (Nikolai, AK) is in USDA hardiness zone 2b on the 2023 map: the coldest night of an average winter reaches −45 to −40 °F (−42.8 to −40 °C).

When is the last frost in Nikolai, AK?

The median last spring frost (32 °F) near 99691 is May 30; after June 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Farewell Lake station.

When is the first frost in Nikolai, AK?

The median first fall frost near 99691 is September 5, giving a median frost-free growing season of 97 days.

When should I plant tomatoes in 99691?

Start tomato seeds indoors around Apr 4 – Apr 18 and set transplants outside around Jun 6 – Jun 20, one to three weeks after the median last frost.

How much rain and snow does 99691 get?

About 15.9 inches of precipitation a year and 96 inches of snowfall (NOAA 1991–2020 normals, Puntilla station).

How hot do summers get in Nikolai, AK?

The average high peaks at 70 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99691 have?

The USDA soil survey maps E28-boreal taiga-gravelly frozen till slopes at the center of ZIP 99691: peat, poorly drained.

What kind of onions grow in Nikolai, AK?

Long-day onions: the longest day near 99691 is 20 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99691 change?

Yes. The 2012 USDA map put 99691 in zone 1b; the 2023 map puts it in zone 2b. The newer map uses 1991–2020 data and more weather stations.