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

Planting zone for 99591 — Saint George Island, AK

ZIP code 99591 (Saint George Island, Aleutians West (CA) County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is May 31 and the first fall frost October 5.

Where ZIP 99591 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 31
First frostOct 5
2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Saint George Island, 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 Saint George Island, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 31median — 50% chance of a later frost
Safe for tender plantsJune 23only 10% chance of frost after
First fall frostOctober 5median — 10% chance by Sep 17
Growing season128 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 9 and returns around October 24.

From the NOAA station St George Island Airport, AK — 4 miles away, elevation 125 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 99591

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 19 – May 3
SpinachSow outdoors · Apr 19 – May 10
Broccoli, cabbageStart indoors · Mar 22 – Apr 5
Broccoli, cabbageTransplant · May 10 – May 24
Onion setsPlant outdoors · May 3 – May 17
PotatoesPlant outdoors · May 10 – May 24
LettuceSow outdoors · May 3 – May 17
Carrots, beetsSow outdoors · May 10 – May 24
TomatoesStart indoors · Apr 5 – Apr 19
TomatoesTransplant · Jun 7 – Jun 21
Peppers, eggplantStart indoors · Mar 22 – Apr 5
Peppers, eggplantTransplant · Jun 14 – Jun 28
BeansSow outdoors · Jun 7 – Jun 21
Sweet cornSow outdoors · Jun 7 – Jun 21
Cucumbers, squashSow outdoors · Jun 7 – Jun 21
Fall lettuce, spinachSow outdoors · Aug 10 – Aug 24
GarlicPlant cloves · Sep 21 – Oct 26
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 31) and first fall frost (Oct 5) 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 Saint George Island, AK.

Soil in Saint George Island, AK

The soil mapped at the center of ZIP 99591 is E26-Maritime dwarf scrub/herbaceous-ashy slopes — stony moderately decomposed plant material, well drained.

TextureStony moderately decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately

Map unit: Aleutian Islands-Western Alaska Peninsula-Maritime Upland-Glaciated Plains.

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 99591; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Saint George Island, AK

Summer high52 °Faverage high, August
Winter low23 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights162nights a year at 32 °F or less
Growing degree days40base 50 °F — the season’s usable heat
Longest day17 h 47 mindaylight on June 21
Shortest day6 h 48 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation20.4 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°32 °FJanuary: average high 30 °F, low 23 °F 30°23° JanFebruary: average high 32 °F, low 24 °F 32°24° FebMarch: average high 31 °F, low 23 °F 31°23° MarApril: average high 35 °F, low 28 °F 35°28° AprMay: average high 42 °F, low 34 °F 42°34° MayJune: average high 47 °F, low 39 °F 47°39° JunJuly: average high 51 °F, low 44 °F 51°44° JulAugust: average high 52 °F, low 46 °F 52°46° AugSeptember: average high 50 °F, low 42 °F 50°42° SepOctober: average high 43 °F, low 36 °F 43°36° OctNovember: average high 38 °F, low 30 °F 38°30° NovDecember: average high 34 °F, low 26 °F 34°26° Dec

Precipitation by month inches

0″1″2″3″January: 1.17 in precipitation 1.2 JanFebruary: 1.06 in precipitation 1.1 FebMarch: 0.80 in precipitation 0.8 MarApril: 0.89 in precipitation 0.9 AprMay: 1.01 in precipitation 1.0 MayJune: 1.26 in precipitation 1.3 JunJuly: 1.97 in precipitation 2.0 JulAugust: 2.66 in precipitation 2.7 AugSeptember: 2.53 in precipitation 2.5 SepOctober: 3.00 in precipitation 3.0 OctNovember: 2.25 in precipitation 2.3 NovDecember: 1.78 in precipitation 1.8 Dec

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

Nearby ZIP codes

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

996606b
Saint Paul Island, AK · 47 mi

Alaska planting zones →

Questions about 99591

What planting zone is ZIP code 99591?

ZIP code 99591 (Saint George Island, 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 Saint George Island, AK?

The median last spring frost (32 °F) near 99591 is May 31; after June 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, St George Island Airport station.

When is the first frost in Saint George Island, AK?

The median first fall frost near 99591 is October 5, giving a median frost-free growing season of 128 days.

When should I plant tomatoes in 99591?

Start tomato seeds indoors around Apr 5 – Apr 19 and set transplants outside around Jun 7 – Jun 21, one to three weeks after the median last frost.

How much rain and snow does 99591 get?

About 20.4 inches of precipitation a year (NOAA 1991–2020 normals, St George Island Airport station).

How hot do summers get in Saint George Island, AK?

The average high peaks at 52 °F in August, with about 0 days a year at 90 °F or more.

What kind of soil does 99591 have?

The USDA soil survey maps E26-Maritime dwarf scrub/herbaceous-ashy slopes at the center of ZIP 99591: stony moderately decomposed plant material, well drained, pH about 5.0 (strongly acidic).

What kind of onions grow in Saint George Island, AK?

Long-day onions: the longest day near 99591 is 17 h 47 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99591 change?

Yes. The 2012 USDA map put 99591 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.