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

Planting zone for 99663 — Seldovia, AK

ZIP code 99663 (Seldovia, Kenai Peninsula County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 10 and the first fall frost October 1.

Where ZIP 99663 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostMay 10
First frostOct 1
2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Seldovia, 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 Seldovia, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 10median — 50% chance of a later frost
Safe for tender plantsMay 24only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 17
Growing season145 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 15.

From the NOAA station Seldovia Airport, AK — 4 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 99663

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 29 – Apr 12
SpinachSow outdoors · Mar 29 – Apr 19
Broccoli, cabbageStart indoors · Mar 1 – Mar 15
Broccoli, cabbageTransplant · Apr 19 – May 3
Onion setsPlant outdoors · Apr 12 – Apr 26
PotatoesPlant outdoors · Apr 19 – May 3
LettuceSow outdoors · Apr 12 – Apr 26
Carrots, beetsSow outdoors · Apr 19 – May 3
TomatoesStart indoors · Mar 15 – Mar 29
TomatoesTransplant · May 17 – May 31
Peppers, eggplantStart indoors · Mar 1 – Mar 15
Peppers, eggplantTransplant · May 24 – Jun 7
BeansSow outdoors · May 17 – May 31
Sweet cornSow outdoors · May 17 – May 31
Cucumbers, squashSow outdoors · May 17 – May 31
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Oct 1) 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 6b in Alaska

286 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 16

Alaska cedar75 ft · blooms mid spring · low shade tolerance · to −22 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack spruce65 ft · blooms late spring · low shade tolerance · to −79 °Flodgepole pine99 ft · blooms mid summer · high shade tolerance · to −70 °Fmountain hemlock125 ft · blooms early summer · low shade tolerance · to −18 °FPacific silver fir165 ft · blooms late spring · low shade tolerance · to −28 °F

Shrubs 49

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FBarclay's willow15 ft · high shade tolerance · to −43 °Fblack crowberry1 ft · blooms mid summer · high shade tolerance · to −43 °Fblack hawthorn15 ft · blooms mid spring · medium shade tolerance · to −47 °Fbog blueberry2 ft · blooms early summer · medium shade tolerance · to −38 °F

Wildflowers & perennials 124

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine aster0.3 ft · blooms early summer · medium shade tolerance · to −28 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °F

Grasses 88

Alaska brome5 ft · blooms late spring · low shade tolerance · to −18 °FAlaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Farctic bluegrass2 ft · high shade tolerance · to −62 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

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 Seldovia, AK.

Soil in Seldovia, AK

The soil mapped at the center of ZIP 99663 is Nanwalek — 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 matter60%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Nanwalek-Rock outcrop complex, 65 to 120 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 99663; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Seldovia, AK

Summer high62 °Faverage high, July
Winter low21 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights167nights a year at 32 °F or less
Growing degree days411base 50 °F — the season’s usable heat
Longest day18 h 39 mindaylight on June 21
Shortest day6 h 03 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.4 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°32 °FJanuary: average high 31 °F, low 21 °F 31°21° JanFebruary: average high 34 °F, low 23 °F 34°23° FebMarch: average high 36 °F, low 24 °F 36°24° MarApril: average high 43 °F, low 31 °F 43°31° AprMay: average high 51 °F, low 37 °F 51°37° MayJune: average high 58 °F, low 44 °F 58°44° JunJuly: average high 62 °F, low 49 °F 62°49° JulAugust: average high 62 °F, low 48 °F 62°48° AugSeptember: average high 55 °F, low 42 °F 55°42° SepOctober: average high 45 °F, low 34 °F 45°34° OctNovember: average high 36 °F, low 27 °F 36°27° NovDecember: average high 33 °F, low 24 °F 33°24° Dec

Precipitation by month inches

0″2″4″6″January: 3.87 in precipitation 3.9 JanFebruary: 3.68 in precipitation 3.7 FebMarch: 3.19 in precipitation 3.2 MarApril: 2.80 in precipitation 2.8 AprMay: 1.15 in precipitation 1.1 MayJune: 1.15 in precipitation 1.1 JunJuly: 1.58 in precipitation 1.6 JulAugust: 2.71 in precipitation 2.7 AugSeptember: 4.09 in precipitation 4.1 SepOctober: 4.60 in precipitation 4.6 OctNovember: 4.83 in precipitation 4.8 NovDecember: 6.74 in precipitation 6.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Seldovia Airport, AK (4 mi away); precipitation: Seldovia Airport, AK (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

996036a
Homer, AK · 18 mi
995566a
Anchor Point, AK · 30 mi
996395b
Ninilchik, AK · 41 mi
996104b
Kasilof, AK · 62 mi
996694b
Soldotna, AK · 70 mi
995685a
Clam Gulch, AK · 70 mi
996724b
Sterling, AK · 86 mi
996115a
Kenai, AK · 104 mi

Alaska planting zones →

Questions about 99663

What planting zone is ZIP code 99663?

ZIP code 99663 (Seldovia, AK) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Seldovia, AK?

The median last spring frost (32 °F) near 99663 is May 10; after May 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Seldovia Airport station.

When is the first frost in Seldovia, AK?

The median first fall frost near 99663 is October 1, giving a median frost-free growing season of 145 days.

When should I plant tomatoes in 99663?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 99663 get?

About 40.4 inches of precipitation a year (NOAA 1991–2020 normals, Seldovia Airport station).

How hot do summers get in Seldovia, AK?

The average high peaks at 62 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99663 have?

The USDA soil survey maps Nanwalek at the center of ZIP 99663: moderately decomposed plant material, well drained, pH about 5.0 (strongly acidic).

What kind of onions grow in Seldovia, AK?

Long-day onions: the longest day near 99663 is 18 h 39 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).