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

Planting zone for 99682 — Tyonek, AK

ZIP code 99682 (Tyonek, Kenai Peninsula County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 18 and the first fall frost September 22.

Where ZIP 99682 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 18
First frostSep 22
2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Tyonek, 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 Tyonek, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 18median — 50% chance of a later frost
Safe for tender plantsMay 30only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 6
Growing season125 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 5 and returns around October 2.

From the NOAA station Kenai 9n, AK — 36 miles away, elevation 125 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 99682

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 6 – Apr 20
SpinachSow outdoors · Apr 6 – Apr 27
Broccoli, cabbageStart indoors · Mar 9 – Mar 23
Broccoli, cabbageTransplant · Apr 27 – May 11
Onion setsPlant outdoors · Apr 20 – May 4
PotatoesPlant outdoors · Apr 27 – May 11
LettuceSow outdoors · Apr 20 – May 4
Carrots, beetsSow outdoors · Apr 27 – May 11
TomatoesStart indoors · Mar 23 – Apr 6
TomatoesTransplant · May 25 – Jun 8
Peppers, eggplantStart indoors · Mar 9 – Mar 23
Peppers, eggplantTransplant · Jun 1 – Jun 15
BeansSow outdoors · May 25 – Jun 8
Sweet cornSow outdoors · May 25 – Jun 8
Cucumbers, squashSow outdoors · May 25 – Jun 8
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 18) 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 Tyonek, AK

The soil mapped at the center of ZIP 99682 is Nancy — moderately decomposed plant material, well drained.

TextureModerately decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter65%high
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of local importanceUSDA classification

Map unit: Nancy-Kashwitna complex, 0 to 2 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 99682; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Tyonek, AK

Summer high63 °Faverage high, July
Winter low8 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights209nights a year at 32 °F or less
Growing degree days478base 50 °F — the season’s usable heat
Longest day19 h 22 mindaylight on June 21
Shortest day5 h 27 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation16.4 inper year, rain and melted snow
Snowfall78 inper year; 154 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°32 °FJanuary: average high 22 °F, low 8 °F 22°8° JanFebruary: average high 28 °F, low 11 °F 28°11° FebMarch: average high 33 °F, low 14 °F 33°14° MarApril: average high 44 °F, low 27 °F 44°27° AprMay: average high 55 °F, low 35 °F 55°35° MayJune: average high 61 °F, low 44 °F 61°44° JunJuly: average high 63 °F, low 49 °F 63°49° JulAugust: average high 62 °F, low 47 °F 62°47° AugSeptember: average high 55 °F, low 39 °F 55°39° SepOctober: average high 43 °F, low 28 °F 43°28° OctNovember: average high 31 °F, low 18 °F 31°18° NovDecember: average high 26 °F, low 12 °F 26°12° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″January: 0.75 in precipitation, 12.4 in snowfall 0.8❄12 JanFebruary: 0.86 in precipitation, 13.4 in snowfall 0.9❄13 FebMarch: 0.69 in precipitation, 11 in snowfall 0.7❄11 MarApril: 0.43 in precipitation, 4 in snowfall 0.4❄4 AprMay: 0.65 in precipitation, 0.3 in snowfall 0.7 MayJune: 1.02 in precipitation 1.0 JunJuly: 1.82 in precipitation 1.8 JulAugust: 2.93 in precipitation 2.9 AugSeptember: 3.10 in precipitation, 0.4 in snowfall 3.1 SepOctober: 1.82 in precipitation, 5.6 in snowfall 1.8❄6 OctNovember: 1.19 in precipitation, 12.6 in snowfall 1.2❄13 NovDecember: 1.16 in precipitation, 18.2 in snowfall 1.2❄18 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kenai 9n, AK (36 mi away); precipitation: Anchorage Intl Airport, AK (39 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

996115a
Kenai, AK · 29 mi
995025b
Anchorage, AK · 40 mi
995305b
Anchorage, AK · 40 mi
995295b
Anchorage, AK · 41 mi
995175b
Anchorage, AK · 41 mi
995095a
Anchorage, AK · 43 mi
995145a
Anchorage, AK · 43 mi
995205b
Anchorage, AK · 43 mi

Alaska planting zones →

Questions about 99682

What planting zone is ZIP code 99682?

ZIP code 99682 (Tyonek, AK) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Tyonek, AK?

The median last spring frost (32 °F) near 99682 is May 18; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kenai 9n station.

When is the first frost in Tyonek, AK?

The median first fall frost near 99682 is September 22, giving a median frost-free growing season of 125 days.

When should I plant tomatoes in 99682?

Start tomato seeds indoors around Mar 23 – Apr 6 and set transplants outside around May 25 – Jun 8, one to three weeks after the median last frost.

How much rain and snow does 99682 get?

About 16.4 inches of precipitation a year and 78 inches of snowfall (NOAA 1991–2020 normals, Anchorage Intl Airport station).

How hot do summers get in Tyonek, AK?

The average high peaks at 63 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99682 have?

The USDA soil survey maps Nancy at the center of ZIP 99682: moderately decomposed plant material, well drained, pH about 5.0 (strongly acidic).

What kind of onions grow in Tyonek, AK?

Long-day onions: the longest day near 99682 is 19 h 22 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99682 change?

Yes. The 2012 USDA map put 99682 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.