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

Planting zone for 99821 — Auke Bay, AK

ZIP code 99821 (Auke Bay, Juneau City and Borough) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 29 and the first fall frost October 20.

Where ZIP 99821 is

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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 29
First frostOct 20
2012 zone7a

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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Auke Bay, 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 Auke Bay, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 29median — 50% chance of a later frost
Safe for tender plantsMay 10only 10% chance of frost after
First fall frostOctober 20median — 10% chance by Oct 2
Growing season173 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 11 and returns around November 7.

From the NOAA station Juneau Mile 17, AK — 4 miles away, elevation 246 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 99821

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 18 – Apr 1
SpinachSow outdoors · Mar 18 – Apr 8
Broccoli, cabbageStart indoors · Feb 18 – Mar 4
Broccoli, cabbageTransplant · Apr 8 – Apr 22
Onion setsPlant outdoors · Apr 1 – Apr 15
PotatoesPlant outdoors · Apr 8 – Apr 22
LettuceSow outdoors · Apr 1 – Apr 15
Carrots, beetsSow outdoors · Apr 8 – Apr 22
TomatoesStart indoors · Mar 4 – Mar 18
TomatoesTransplant · May 6 – May 20
Peppers, eggplantStart indoors · Feb 18 – Mar 4
Peppers, eggplantTransplant · May 13 – May 27
BeansSow outdoors · May 6 – May 20
Sweet cornSow outdoors · May 6 – May 20
Cucumbers, squashSow outdoors · May 6 – May 20
Fall lettuce, spinachSow outdoors · Aug 25 – Sep 8
GarlicPlant cloves · Oct 6 – Nov 10
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 29) and first fall frost (Oct 20) 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 7a in Alaska

289 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. 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 50

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 125

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 89

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 Auke Bay, AK.

Soil in Auke Bay, AK

The soil mapped at the center of ZIP 99821 is Cryohemists — peat, very poorly drained.

TexturePeattop layer
pH4.8strongly acidic; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter94.5%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Cryohemists, rolling lowlands, 6 to 35 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 99821; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Auke Bay, AK

Summer high63 °Faverage high, July
Winter low25 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights134nights a year at 32 °F or less
Growing degree days693base 50 °F — the season’s usable heat
Longest day18 h 19 mindaylight on June 21
Shortest day6 h 20 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation62.3 inper year, rain and melted snow
Snowfall77 inper year; 74 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°32 °FJanuary: average high 33 °F, low 25 °F 33°25° JanFebruary: average high 35 °F, low 27 °F 35°27° FebMarch: average high 39 °F, low 28 °F 39°28° MarApril: average high 47 °F, low 34 °F 47°34° AprMay: average high 57 °F, low 41 °F 57°41° MayJune: average high 62 °F, low 48 °F 62°48° JunJuly: average high 63 °F, low 51 °F 63°51° JulAugust: average high 63 °F, low 51 °F 63°51° AugSeptember: average high 56 °F, low 45 °F 56°45° SepOctober: average high 47 °F, low 38 °F 47°38° OctNovember: average high 38 °F, low 31 °F 38°31° NovDecember: average high 35 °F, low 28 °F 35°28° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″10″January: 5.77 in precipitation, 24.2 in snowfall 5.8❄24 JanFebruary: 3.80 in precipitation, 11.3 in snowfall 3.8❄11 FebMarch: 3.16 in precipitation, 9.9 in snowfall 3.2❄10 MarApril: 2.47 in precipitation, 1.1 in snowfall 2.5❄1 AprMay: 3.30 in precipitation 3.3 MayJune: 3.74 in precipitation 3.7 JunJuly: 5.01 in precipitation 5.0 JulAugust: 6.13 in precipitation 6.1 AugSeptember: 9.03 in precipitation 9.0 SepOctober: 7.74 in precipitation, 0.7 in snowfall 7.7❄1 OctNovember: 6.25 in precipitation, 12.1 in snowfall 6.3❄12 NovDecember: 5.86 in precipitation, 18.1 in snowfall 5.9❄18 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Juneau Mile 17, AK (4 mi away); precipitation: Juneau Lena Pt, AK (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

998127a
Juneau, AK · 12 mi
998027a
Juneau, AK · 14 mi
998037a
Juneau, AK · 14 mi
998117a
Juneau, AK · 14 mi
998247a
Douglas, AK · 17 mi
998016a
Juneau, AK · 20 mi
998507a
Juneau, AK · 28 mi
998297a
Hoonah, AK · 37 mi

Alaska planting zones →

Questions about 99821

What planting zone is ZIP code 99821?

ZIP code 99821 (Auke Bay, AK) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Auke Bay, AK?

The median last spring frost (32 °F) near 99821 is April 29; after May 10 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Juneau Mile 17 station.

When is the first frost in Auke Bay, AK?

The median first fall frost near 99821 is October 20, giving a median frost-free growing season of 173 days.

When should I plant tomatoes in 99821?

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

How much rain and snow does 99821 get?

About 62.3 inches of precipitation a year and 77 inches of snowfall (NOAA 1991–2020 normals, Juneau Lena Pt station).

How hot do summers get in Auke Bay, 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 99821 have?

The USDA soil survey maps Cryohemists at the center of ZIP 99821: peat, very poorly drained, pH about 4.8 (strongly acidic).

What kind of onions grow in Auke Bay, AK?

Long-day onions: the longest day near 99821 is 18 h 19 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).