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

Planting zone for 99667 — Skwentna, AK

ZIP code 99667 (Skwentna, Matanuska-Susitna Borough) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is June 2 and the first fall frost September 8.

Where ZIP 99667 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 frostJun 2

First frostSep 8

2012 zone3a

Was 3a on the 2012 map — 1.5 zones warmer now. 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 Skwentna, 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 Skwentna, AK

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 2median — 50% chance of a later frost

Safe for tender plantsJune 11only 10% chance of frost after

First fall frostSeptember 8median — 10% chance by Aug 23

Growing season98 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 21 and returns around September 22.

From the NOAA station Hayes River, AK — 20 miles away, elevation 1,001 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 99667

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 21 – May 5

SpinachSow outdoors · Apr 21 – May 12

Broccoli, cabbageStart indoors · Mar 24 – Apr 7

Broccoli, cabbageTransplant · May 12 – May 26

Onion setsPlant outdoors · May 5 – May 19

PotatoesPlant outdoors · May 12 – May 26

LettuceSow outdoors · May 5 – May 19

Carrots, beetsSow outdoors · May 12 – May 26

TomatoesStart indoors · Apr 7 – Apr 21

TomatoesTransplant · Jun 9 – Jun 23

Peppers, eggplantStart indoors · Mar 24 – Apr 7

Peppers, eggplantTransplant · Jun 16 – Jun 30

BeansSow outdoors · Jun 9 – Jun 23

Sweet cornSow outdoors · Jun 9 – Jun 23

Cucumbers, squashSow outdoors · Jun 9 – Jun 23

Fall lettuce, spinachSow outdoors · Jul 14 – Jul 28

GarlicPlant cloves · Aug 25 – Sep 29

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 2) and first fall frost (Sep 8) 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 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.

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 Skwentna, AK.

Soil in Skwentna, AK

The soil mapped at the center of ZIP 99667 is E23-boreal subalpine scrub/meadow mosaic-silty acid slopes — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter75%high

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Cook Inlet Mountains-Boreal Subalpine and Alpine-Mountains, Acid.

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 99667; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Skwentna, AK

Summer high69 °Faverage high, July

Winter low5 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights230nights a year at 32 °F or less

Growing degree days617base 50 °F — the season’s usable heat

Longest day19 h 36 mindaylight on June 21

Shortest day5 h 16 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: Hayes River, AK (20 mi away); precipitation: Puntilla, AK (34 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Soldotna, AK · 100 mi

996104b

Kasilof, AK · 102 mi

995685a

Clam Gulch, AK · 111 mi

Alaska planting zones →

Questions about 99667

What planting zone is ZIP code 99667?

ZIP code 99667 (Skwentna, 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).

When is the last frost in Skwentna, AK?

The median last spring frost (32 °F) near 99667 is June 2; after June 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hayes River station.

When is the first frost in Skwentna, AK?

The median first fall frost near 99667 is September 8, giving a median frost-free growing season of 98 days.

When should I plant tomatoes in 99667?

Start tomato seeds indoors around Apr 7 – Apr 21 and set transplants outside around Jun 9 – Jun 23, one to three weeks after the median last frost.

How much rain and snow does 99667 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 Skwentna, AK?

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

What kind of soil does 99667 have?

The USDA soil survey maps E23-boreal subalpine scrub/meadow mosaic-silty acid slopes at the center of ZIP 99667: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

What kind of onions grow in Skwentna, AK?

Long-day onions: the longest day near 99667 is 19 h 36 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99667 change?

Yes. The 2012 USDA map put 99667 in zone 3a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.