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

Planting zone for 99599 — Anchorage, AK

ZIP code 99599 (Anchorage, Anchorage Municipality) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 1 and the first fall frost September 29.

Where ZIP 99599 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 1
First frostSep 29
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 Anchorage, 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 Anchorage, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 1median — 50% chance of a later frost
Safe for tender plantsMay 9only 10% chance of frost after
First fall frostSeptember 29median — 10% chance by Sep 17
Growing season150 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 19 and returns around October 8.

From the NOAA station Anchorage Merrill Field, AK — 2 miles away, elevation 138 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 99599

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 20 – Apr 3
SpinachSow outdoors · Mar 20 – Apr 10
Broccoli, cabbageStart indoors · Feb 20 – Mar 6
Broccoli, cabbageTransplant · Apr 10 – Apr 24
Onion setsPlant outdoors · Apr 3 – Apr 17
PotatoesPlant outdoors · Apr 10 – Apr 24
LettuceSow outdoors · Apr 3 – Apr 17
Carrots, beetsSow outdoors · Apr 10 – Apr 24
TomatoesStart indoors · Mar 6 – Mar 20
TomatoesTransplant · May 8 – May 22
Peppers, eggplantStart indoors · Feb 20 – Mar 6
Peppers, eggplantTransplant · May 15 – May 29
BeansSow outdoors · May 8 – May 22
Sweet cornSow outdoors · May 8 – May 22
Cucumbers, squashSow outdoors · May 8 – May 22
Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18
GarlicPlant cloves · Sep 15 – Oct 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 1) and first fall frost (Sep 29) 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 5a in Alaska

275 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. Each links to its USDA PLANTS profile.

Trees 14

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 °FPacific silver fir165 ft · blooms late spring · low shade tolerance · to −28 °Fpaper birch70 ft · blooms mid spring · high shade tolerance · to −62 °F

Shrubs 46

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 119

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 87

Alaska 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 °Fbeaked sedge4 ft · blooms late 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 Anchorage, AK.

Soil in Anchorage, AK

The soil mapped at the center of ZIP 99599 is Cryorthents — very gravelly sandy loam, somewhat excessively drained.

TextureVery gravelly sandy loamdrains and warms fast; dries out and needs more feeding
pH6.3slightly acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter1%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Cryorthents and Urban land, 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 99599; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Anchorage, AK

Summer high68 °Faverage high, July
Winter low8 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights184nights a year at 32 °F or less
Growing degree days958base 50 °F — the season’s usable heat
Longest day19 h 22 mindaylight on June 21
Shortest day5 h 28 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation14.2 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 23 °F, low 8 °F 23°8° JanFebruary: average high 28 °F, low 12 °F 28°12° FebMarch: average high 34 °F, low 17 °F 34°17° MarApril: average high 47 °F, low 30 °F 47°30° AprMay: average high 58 °F, low 41 °F 58°41° MayJune: average high 66 °F, low 50 °F 66°50° JunJuly: average high 68 °F, low 54 °F 68°54° JulAugust: average high 66 °F, low 51 °F 66°51° AugSeptember: average high 57 °F, low 43 °F 57°43° SepOctober: average high 43 °F, low 30 °F 43°30° OctNovember: average high 29 °F, low 16 °F 29°16° NovDecember: average high 25 °F, low 11 °F 25°11° Dec

Precipitation by month inches

0″1″2″3″4″January: 0.46 in precipitation 0.5 JanFebruary: 0.71 in precipitation 0.7 FebMarch: 0.54 in precipitation 0.5 MarApril: 0.30 in precipitation 0.3 AprMay: 0.62 in precipitation 0.6 MayJune: 0.99 in precipitation 1.0 JunJuly: 1.70 in precipitation 1.7 JulAugust: 2.48 in precipitation 2.5 AugSeptember: 3.02 in precipitation 3.0 SepOctober: 1.57 in precipitation 1.6 OctNovember: 0.88 in precipitation 0.9 NovDecember: 0.89 in precipitation 0.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Anchorage Merrill Field, AK (2 mi away); precipitation: Anchorage Merrill Field, AK (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

995135b
Anchorage, AK · 2 mi
995185a
Anchorage, AK · 2 mi
995175b
Anchorage, AK · 2 mi
995095a
Anchorage, AK · 2 mi
995145a
Anchorage, AK · 2 mi
995205b
Anchorage, AK · 2 mi
995215a
Anchorage, AK · 2 mi
995225a
Anchorage, AK · 2 mi

All 25 ZIP codes in Anchorage → · Alaska planting zones →

Questions about 99599

What planting zone is ZIP code 99599?

ZIP code 99599 (Anchorage, 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 Anchorage, AK?

The median last spring frost (32 °F) near 99599 is May 1; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Anchorage Merrill Field station.

When is the first frost in Anchorage, AK?

The median first fall frost near 99599 is September 29, giving a median frost-free growing season of 150 days.

When should I plant tomatoes in 99599?

Start tomato seeds indoors around Mar 6 – Mar 20 and set transplants outside around May 8 – May 22, one to three weeks after the median last frost.

How much rain and snow does 99599 get?

About 14.2 inches of precipitation a year (NOAA 1991–2020 normals, Anchorage Merrill Field station).

How hot do summers get in Anchorage, AK?

The average high peaks at 68 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99599 have?

The USDA soil survey maps Cryorthents at the center of ZIP 99599: very gravelly sandy loam, somewhat excessively drained, pH about 6.3 (slightly acidic).

What kind of onions grow in Anchorage, AK?

Long-day onions: the longest day near 99599 is 19 h 22 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99599 change?

Yes. The 2012 USDA map put 99599 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.