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

Planting zone for 99577 — Eagle River, AK

ZIP code 99577 (Eagle River, Anchorage Municipality) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 16 and the first fall frost September 20.

Where ZIP 99577 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 16
First frostSep 20
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 Eagle River, 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 Eagle River, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 16median — 50% chance of a later frost
Safe for tender plantsJune 9only 10% chance of frost after
First fall frostSeptember 20median — 10% chance by Sep 4
Growing season125 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 1.

From the NOAA station Eagle Rvr Nature Center, AK — 4 miles away, elevation 522 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 99577

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 4 – Apr 18
SpinachSow outdoors · Apr 4 – Apr 25
Broccoli, cabbageStart indoors · Mar 7 – Mar 21
Broccoli, cabbageTransplant · Apr 25 – May 9
Onion setsPlant outdoors · Apr 18 – May 2
PotatoesPlant outdoors · Apr 25 – May 9
LettuceSow outdoors · Apr 18 – May 2
Carrots, beetsSow outdoors · Apr 25 – May 9
TomatoesStart indoors · Mar 21 – Apr 4
TomatoesTransplant · May 23 – Jun 6
Peppers, eggplantStart indoors · Mar 7 – Mar 21
Peppers, eggplantTransplant · May 30 – Jun 13
BeansSow outdoors · May 23 – Jun 6
Sweet cornSow outdoors · May 23 – Jun 6
Cucumbers, squashSow outdoors · May 23 – Jun 6
Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9
GarlicPlant cloves · Sep 6 – Oct 11
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 16) and first fall frost (Sep 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 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 Eagle River, AK.

Soil in Eagle River, AK

The soil mapped at the center of ZIP 99577 is E23-boreal alpine dwarf scrub-gravelly colluvial slopes — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH4.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately

Map unit: Cook Inlet Mountains-Boreal Alpine-Barren Mountains.

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 99577; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Eagle River, AK

Summer high67 °Faverage high, July
Winter low6 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights204nights a year at 32 °F or less
Growing degree days587base 50 °F — the season’s usable heat
Longest day19 h 21 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)
Precipitation22.6 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 21 °F, low 6 °F 21°6° JanFebruary: average high 28 °F, low 12 °F 28°12° FebMarch: average high 35 °F, low 15 °F 35°15° MarApril: average high 47 °F, low 27 °F 47°27° AprMay: average high 58 °F, low 36 °F 58°36° MayJune: average high 65 °F, low 44 °F 65°44° JunJuly: average high 67 °F, low 48 °F 67°48° JulAugust: average high 65 °F, low 45 °F 65°45° AugSeptember: average high 56 °F, low 37 °F 56°37° SepOctober: average high 42 °F, low 26 °F 42°26° OctNovember: average high 26 °F, low 13 °F 26°13° NovDecember: average high 23 °F, low 9 °F 23°9° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.26 in precipitation 2.3 JanFebruary: 1.64 in precipitation 1.6 FebMarch: 1.56 in precipitation 1.6 MarApril: 0.76 in precipitation 0.8 AprMay: 0.94 in precipitation 0.9 MayJune: 1.31 in precipitation 1.3 JunJuly: 1.68 in precipitation 1.7 JulAugust: 2.62 in precipitation 2.6 AugSeptember: 3.64 in precipitation 3.6 SepOctober: 2.46 in precipitation 2.5 OctNovember: 1.72 in precipitation 1.7 NovDecember: 1.96 in precipitation 2.0 Dec

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

Nearby ZIP codes

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

995045a
Anchorage, AK · 11 mi
995405b
Indian, AK · 11 mi
995075a
Anchorage, AK · 12 mi
995675a
Chugiak, AK · 12 mi
995055a
Jber, AK · 14 mi
995165b
Anchorage, AK · 16 mi
995085a
Anchorage, AK · 18 mi
995065a
Jber, AK · 19 mi

Alaska planting zones →

Questions about 99577

What planting zone is ZIP code 99577?

ZIP code 99577 (Eagle River, 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 Eagle River, AK?

The median last spring frost (32 °F) near 99577 is May 16; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Eagle Rvr Nature Center station.

When is the first frost in Eagle River, AK?

The median first fall frost near 99577 is September 20, giving a median frost-free growing season of 125 days.

When should I plant tomatoes in 99577?

Start tomato seeds indoors around Mar 21 – Apr 4 and set transplants outside around May 23 – Jun 6, one to three weeks after the median last frost.

How much rain and snow does 99577 get?

About 22.6 inches of precipitation a year (NOAA 1991–2020 normals, Eagle Rvr Nature Center station).

How hot do summers get in Eagle River, AK?

The average high peaks at 67 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99577 have?

The USDA soil survey maps E23-boreal alpine dwarf scrub-gravelly colluvial slopes at the center of ZIP 99577: slightly decomposed plant material, well drained, pH about 4.0 (strongly acidic).

What kind of onions grow in Eagle River, AK?

Long-day onions: the longest day near 99577 is 19 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99577 change?

Yes. The 2012 USDA map put 99577 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.