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

Planting zone for 99850 — Juneau, AK

ZIP code 99850 (Juneau, Juneau City and Borough) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is May 28 and the first fall frost September 25.

Where ZIP 99850 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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostMay 28
First frostSep 25
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 Juneau, 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 Juneau, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 28median — 50% chance of a later frost
Safe for tender plantsJune 12only 10% chance of frost after
First fall frostSeptember 25median — 10% chance by Aug 29
Growing season116 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 13 and returns around October 5.

From the NOAA station Gustavus 2 Ne, AK — 9 miles away, elevation 20 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 99850

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 16 – Apr 30
SpinachSow outdoors · Apr 16 – May 7
Broccoli, cabbageStart indoors · Mar 19 – Apr 2
Broccoli, cabbageTransplant · May 7 – May 21
Onion setsPlant outdoors · Apr 30 – May 14
PotatoesPlant outdoors · May 7 – May 21
LettuceSow outdoors · Apr 30 – May 14
Carrots, beetsSow outdoors · May 7 – May 21
TomatoesStart indoors · Apr 2 – Apr 16
TomatoesTransplant · Jun 4 – Jun 18
Peppers, eggplantStart indoors · Mar 19 – Apr 2
Peppers, eggplantTransplant · Jun 11 – Jun 25
BeansSow outdoors · Jun 4 – Jun 18
Sweet cornSow outdoors · Jun 4 – Jun 18
Cucumbers, squashSow outdoors · Jun 4 – Jun 18
Fall lettuce, spinachSow outdoors · Jul 31 – Aug 14
GarlicPlant cloves · Sep 11 – Oct 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 28) and first fall frost (Sep 25) 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 Juneau, AK.

Soil in Juneau, AK

The soil mapped at the center of ZIP 99850 is Tuxekan — moderately decomposed plant material, well drained.

TextureModerately decomposed plant materialtop layer
pH3.8strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter80%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Tuxekan silt loam, alluvial fans, 0 to 5 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 99850; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Juneau, AK

Summer high63 °Faverage high, July
Winter low22 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights163nights a year at 32 °F or less
Growing degree days421base 50 °F — the season’s usable heat
Longest day18 h 20 mindaylight on June 21
Shortest day6 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation58.7 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°32 °FJanuary: average high 33 °F, low 22 °F 33°22° JanFebruary: average high 37 °F, low 23 °F 37°23° FebMarch: average high 40 °F, low 24 °F 40°24° MarApril: average high 49 °F, low 29 °F 49°29° AprMay: average high 57 °F, low 35 °F 57°35° MayJune: average high 62 °F, low 42 °F 62°42° JunJuly: average high 63 °F, low 47 °F 63°47° JulAugust: average high 63 °F, low 46 °F 63°46° AugSeptember: average high 56 °F, low 41 °F 56°41° SepOctober: average high 48 °F, low 34 °F 48°34° OctNovember: average high 39 °F, low 28 °F 39°28° NovDecember: average high 35 °F, low 24 °F 35°24° Dec

Precipitation by month inches

0″2″4″6″8″January: 4.94 in precipitation 4.9 JanFebruary: 3.62 in precipitation 3.6 FebMarch: 3.50 in precipitation 3.5 MarApril: 2.80 in precipitation 2.8 AprMay: 2.75 in precipitation 2.8 MayJune: 2.50 in precipitation 2.5 JunJuly: 4.19 in precipitation 4.2 JulAugust: 5.69 in precipitation 5.7 AugSeptember: 7.64 in precipitation 7.6 SepOctober: 8.25 in precipitation 8.3 OctNovember: 6.31 in precipitation 6.3 NovDecember: 6.50 in precipitation 6.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Gustavus 2 Ne, AK (9 mi away); precipitation: Gustavus 2 Ne, AK (9 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.

998267a
Gustavus, AK · 13 mi
998217a
Auke Bay, AK · 28 mi
998297a
Hoonah, AK · 33 mi
998275b
Haines, AK · 35 mi
998417a
Tenakee Springs, AK · 37 mi
998127a
Juneau, AK · 38 mi
998257a
Elfin Cove, AK · 40 mi
998027a
Juneau, AK · 41 mi

All 6 ZIP codes in Juneau → · Alaska planting zones →

Questions about 99850

What planting zone is ZIP code 99850?

ZIP code 99850 (Juneau, 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 Juneau, AK?

The median last spring frost (32 °F) near 99850 is May 28; after June 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Gustavus 2 Ne station.

When is the first frost in Juneau, AK?

The median first fall frost near 99850 is September 25, giving a median frost-free growing season of 116 days.

When should I plant tomatoes in 99850?

Start tomato seeds indoors around Apr 2 – Apr 16 and set transplants outside around Jun 4 – Jun 18, one to three weeks after the median last frost.

How much rain and snow does 99850 get?

About 58.7 inches of precipitation a year (NOAA 1991–2020 normals, Gustavus 2 Ne station).

How hot do summers get in Juneau, 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 99850 have?

The USDA soil survey maps Tuxekan at the center of ZIP 99850: moderately decomposed plant material, well drained, pH about 3.8 (strongly acidic).

What kind of onions grow in Juneau, AK?

Long-day onions: the longest day near 99850 is 18 h 20 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).