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

Planting zone for 99731 — Fort Greely, AK

ZIP code 99731 (Fort Greely, Southeast Fairbanks Census Area County) is in USDA zone 2a: the coldest winter night averages −50 to −45 °F. The median last spring frost is May 26 and the first fall frost September 2.

Where ZIP 99731 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.

Zone2a−50 to −45 °F
Coldest night−45.6 to −42.8 °C
Last frostMay 26
First frostSep 2
2012 zone2a

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 2a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Fort Greely, 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 Fort Greely, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 26median — 50% chance of a later frost
Safe for tender plantsJune 9only 10% chance of frost after
First fall frostSeptember 2median — 10% chance by Aug 19
Growing season98 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 15 and returns around September 16.

From the NOAA station Whitestone Farms, AK — 22 miles away, elevation 994 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 99731

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 14 – Apr 28
SpinachSow outdoors · Apr 14 – May 5
Broccoli, cabbageStart indoors · Mar 17 – Mar 31
Broccoli, cabbageTransplant · May 5 – May 19
Onion setsPlant outdoors · Apr 28 – May 12
PotatoesPlant outdoors · May 5 – May 19
LettuceSow outdoors · Apr 28 – May 12
Carrots, beetsSow outdoors · May 5 – May 19
TomatoesStart indoors · Mar 31 – Apr 14
TomatoesTransplant · Jun 2 – Jun 16
Peppers, eggplantStart indoors · Mar 17 – Mar 31
Peppers, eggplantTransplant · Jun 9 – Jun 23
BeansSow outdoors · Jun 2 – Jun 16
Sweet cornSow outdoors · Jun 2 – Jun 16
Cucumbers, squashSow outdoors · Jun 2 – Jun 16
Fall lettuce, spinachSow outdoors · Jul 8 – Jul 22
GarlicPlant cloves · Aug 19 – Sep 23
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 26) and first fall frost (Sep 2) 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 2a in Alaska

44 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −50 °F or colder — the bottom of zone 2a. Each links to its USDA PLANTS profile.

Trees 8

balsam 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 °Fpaper birch70 ft · blooms mid spring · high shade tolerance · to −62 °Fquaking aspen65 ft · blooms mid spring · high shade tolerance · to −70 °Fsubalpine fir90 ft · blooms late spring · low shade tolerance · to −51 °F

Shrubs 16

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °Fhalberd willow3 ft · blooms early summer · to −62 °FLapland rosebay3 ft · blooms late spring · low shade tolerance · to −62 °Flingonberry0.5 ft · blooms summer · high shade tolerance · to −62 °FMacKenzie's willow45 ft · blooms early spring · high shade tolerance · to −50 °Fmarsh Labrador tea0.5 ft · blooms summer · to −62 °F

Wildflowers & perennials 12

alpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °Farctic dock1 ft · blooms summer · high shade tolerance · to −62 °Farctic lupine2 ft · blooms spring · medium shade tolerance · to −62 °Farctic poppy1.5 ft · blooms summer · low shade tolerance · to −54 °Farctic raspberry1 ft · blooms summer · high shade tolerance · to −62 °Feightpetal mountain-avens0.3 ft · blooms late spring · medium shade tolerance · to −62 °F

Grasses 6

arctic bluegrass2 ft · high shade tolerance · to −62 °FHoppner's sedge1 ft · high shade tolerance · to −52 °Flargeflower speargrass2 ft · high shade tolerance · to −52 °Flivid sedge1 ft · blooms early summer · high shade tolerance · to −62 °FLyngbye's sedge1 ft · high shade tolerance · to −52 °FRamensk's sedge1 ft · high shade tolerance · to −52 °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 Fort Greely, AK.

Soil in Fort Greely, AK

The soil mapped at the center of ZIP 99731 is Histels — mucky peat, poorly drained.

TextureMucky peattop layer
pH4.8strongly acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter85%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Histels, impact area.

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 99731; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fort Greely, AK

Summer high74 °Faverage high, July
Winter low−11 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights232nights a year at 32 °F or less
Growing degree days893base 50 °F — the season’s usable heat
Longest day20 h 59 mindaylight on June 21
Shortest day4 h 13 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation12.7 inper year, rain and melted snow
Snowfall42 inper year; 179 days with snow on the ground

Average high and low, by month

−20°−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 6 °F, low -11 °F 6°−11° JanFebruary: average high 16 °F, low -4 °F 16°−4° FebMarch: average high 27 °F, low 1 °F 27°1° MarApril: average high 48 °F, low 21 °F 48°21° AprMay: average high 63 °F, low 34 °F 63°34° MayJune: average high 73 °F, low 45 °F 73°45° JunJuly: average high 74 °F, low 49 °F 74°49° JulAugust: average high 67 °F, low 44 °F 67°44° AugSeptember: average high 56 °F, low 35 °F 56°35° SepOctober: average high 34 °F, low 18 °F 34°18° OctNovember: average high 15 °F, low -1 °F 15°−1° NovDecember: average high 10 °F, low -8 °F 10°−8° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.44 in precipitation, 5.7 in snowfall 0.4❄6 JanFebruary: 0.32 in precipitation, 5 in snowfall 0.3❄5 FebMarch: 0.33 in precipitation, 3.7 in snowfall 0.3❄4 MarApril: 0.24 in precipitation, 1.6 in snowfall 0.2❄2 AprMay: 0.84 in precipitation, 1.1 in snowfall 0.8❄1 MayJune: 2.51 in precipitation 2.5 JunJuly: 2.75 in precipitation 2.8 JulAugust: 2.13 in precipitation 2.1 AugSeptember: 1.16 in precipitation, 1.7 in snowfall 1.2❄2 SepOctober: 0.80 in precipitation, 7.3 in snowfall 0.8❄7 OctNovember: 0.66 in precipitation, 8.7 in snowfall 0.7❄9 NovDecember: 0.51 in precipitation, 6.7 in snowfall 0.5❄7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Whitestone Farms, AK (22 mi away); precipitation: Whitestone Farms, AK (22 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.

997143b
Salcha, AK · 30 mi
997373a
Delta Junction, AK · 50 mi
997022a
Eielson Afb, AK · 51 mi
997052a
North Pole, AK · 62 mi
997162a
Two Rivers, AK · 65 mi
997032a
Fort Wainwright, AK · 70 mi
997102b
Fairbanks, AK · 72 mi
997112a
Fairbanks, AK · 72 mi

Alaska planting zones →

Questions about 99731

What planting zone is ZIP code 99731?

ZIP code 99731 (Fort Greely, AK) is in USDA hardiness zone 2a on the 2023 map: the coldest night of an average winter reaches −50 to −45 °F (−45.6 to −42.8 °C).

When is the last frost in Fort Greely, AK?

The median last spring frost (32 °F) near 99731 is May 26; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Whitestone Farms station.

When is the first frost in Fort Greely, AK?

The median first fall frost near 99731 is September 2, giving a median frost-free growing season of 98 days.

When should I plant tomatoes in 99731?

Start tomato seeds indoors around Mar 31 – Apr 14 and set transplants outside around Jun 2 – Jun 16, one to three weeks after the median last frost.

How much rain and snow does 99731 get?

About 12.7 inches of precipitation a year and 42 inches of snowfall (NOAA 1991–2020 normals, Whitestone Farms station).

How hot do summers get in Fort Greely, AK?

The average high peaks at 74 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99731 have?

The USDA soil survey maps Histels at the center of ZIP 99731: mucky peat, poorly drained, pH about 4.8 (strongly acidic).

What kind of onions grow in Fort Greely, AK?

Long-day onions: the longest day near 99731 is 20 h 59 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).