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

Planting zone for 99768 — Ruby, AK

ZIP code 99768 (Ruby, Yukon-Koyukuk (CA) County) is in USDA zone 3a: the coldest winter night averages −40 to −35 °F. The median last spring frost is May 29 and the first fall frost August 28.

Where ZIP 99768 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.

Zone3a−40 to −35 °F
Coldest night−40 to −37.2 °C
Last frostMay 29
First frostAug 28
2012 zone2a

Was 2a on the 2012 map — a full zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 3a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Ruby, 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 Ruby, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 29median — 50% chance of a later frost
Safe for tender plantsJune 16only 10% chance of frost after
First fall frostAugust 28median — 10% chance by Aug 10
Growing season89 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 16 and returns around September 8.

From the NOAA station Tanana Calhoun Mem Airport, AK — 43 miles away, elevation 226 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 99768

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 17 – May 1
SpinachSow outdoors · Apr 17 – May 8
Broccoli, cabbageStart indoors · Mar 20 – Apr 3
Broccoli, cabbageTransplant · May 8 – May 22
Onion setsPlant outdoors · May 1 – May 15
PotatoesPlant outdoors · May 8 – May 22
LettuceSow outdoors · May 1 – May 15
Carrots, beetsSow outdoors · May 8 – May 22
TomatoesStart indoors · Apr 3 – Apr 17
TomatoesTransplant · Jun 5 – Jun 19
Peppers, eggplantStart indoors · Mar 20 – Apr 3
Peppers, eggplantTransplant · Jun 12 – Jun 26
BeansSow outdoors · Jun 5 – Jun 19
Sweet cornSow outdoors · Jun 5 – Jun 19
Cucumbers, squashSow outdoors · Jun 5 – Jun 19
Fall lettuce, spinachSow outdoors · Jul 3 – Jul 17
GarlicPlant cloves · Aug 14 – Sep 18
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 29) and first fall frost (Aug 28) 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 3a in Alaska

80 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −40 °F or colder — the bottom of zone 3a. 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 26

alpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °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 °Fchokecherry25 ft · blooms mid spring · high shade tolerance · to −43 °Fcommon juniper10 ft · blooms mid spring · high shade tolerance · to −43 °F

Wildflowers & perennials 22

alpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine 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 °F

Grasses 19

alpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Farctic bluegrass2 ft · high shade tolerance · to −62 °FBigelow's sedge0.4 ft · blooms mid summer · medium shade tolerance · to −43 °Fglaucous bluegrass2 ft · blooms mid summer · high shade tolerance · to −40 °Fhair-like sedge1.7 ft · blooms late spring · low shade tolerance · to −43 °FHoppner'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 Ruby, AK.

Soil in Ruby, AK

The soil mapped at the center of ZIP 99768 is E31-Boreal forest-silty slopes — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH3.5strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupAwater soaks in fast
Farmland classNot prime farmlandUSDA classification

Map unit: Interior Alaska Highlands-Boreal Upland-Rounded Mountains, Acid.

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 99768; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ruby, AK

Summer high71 °Faverage high, July
Winter low−17 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights236nights a year at 32 °F or less
Growing degree days742base 50 °F — the season’s usable heat
Longest day22 h 25 mindaylight on June 21
Shortest day3 h 23 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation11.5 inper year, rain and melted snow
Snowfall50 inper year; 196 days with snow on the ground

Average high and low, by month

−30°−20°−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high -1 °F, low -17 °F −1°−17° JanFebruary: average high 8 °F, low -11 °F 8°−11° FebMarch: average high 19 °F, low -6 °F 19°−6° MarApril: average high 39 °F, low 16 °F 39°16° AprMay: average high 59 °F, low 33 °F 59°33° MayJune: average high 70 °F, low 45 °F 70°45° JunJuly: average high 71 °F, low 49 °F 71°49° JulAugust: average high 64 °F, low 43 °F 64°43° AugSeptember: average high 52 °F, low 34 °F 52°34° SepOctober: average high 31 °F, low 17 °F 31°17° OctNovember: average high 11 °F, low -4 °F 11°−4° NovDecember: average high 2 °F, low -13 °F 2°−13° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.38 in precipitation, 7.7 in snowfall 0.4❄8 JanFebruary: 0.44 in precipitation, 8 in snowfall 0.4❄8 FebMarch: 0.24 in precipitation, 5.4 in snowfall 0.2❄5 MarApril: 0.30 in precipitation, 2.5 in snowfall 0.3❄3 AprMay: 0.64 in precipitation, 0.3 in snowfall 0.6 MayJune: 1.48 in precipitation 1.5 JunJuly: 1.95 in precipitation 1.9 JulAugust: 2.68 in precipitation 2.7 AugSeptember: 1.68 in precipitation, 0.8 in snowfall 1.7❄1 SepOctober: 0.71 in precipitation, 5 in snowfall 0.7❄5 OctNovember: 0.56 in precipitation, 10 in snowfall 0.6❄10 NovDecember: 0.41 in precipitation, 10.3 in snowfall 0.4❄10 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Tanana Calhoun Mem Airport, AK (43 mi away); precipitation: Tanana Calhoun Mem Airport, AK (43 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

4 of the 4 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

997771b
Tanana, AK · 44 mi
997451b
Hughes, AK · 58 mi
997201a
Allakaket, AK · 93 mi
997572b
Lake Minchumina, AK · 107 mi

Alaska planting zones →

Questions about 99768

What planting zone is ZIP code 99768?

ZIP code 99768 (Ruby, AK) is in USDA hardiness zone 3a on the 2023 map: the coldest night of an average winter reaches −40 to −35 °F (−40 to −37.2 °C).

When is the last frost in Ruby, AK?

The median last spring frost (32 °F) near 99768 is May 29; after June 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Tanana Calhoun Mem Airport station.

When is the first frost in Ruby, AK?

The median first fall frost near 99768 is August 28, giving a median frost-free growing season of 89 days.

When should I plant tomatoes in 99768?

Start tomato seeds indoors around Apr 3 – Apr 17 and set transplants outside around Jun 5 – Jun 19, one to three weeks after the median last frost.

How much rain and snow does 99768 get?

About 11.5 inches of precipitation a year and 50 inches of snowfall (NOAA 1991–2020 normals, Tanana Calhoun Mem Airport station).

How hot do summers get in Ruby, AK?

The average high peaks at 71 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99768 have?

The USDA soil survey maps E31-Boreal forest-silty slopes at the center of ZIP 99768: slightly decomposed plant material, well drained, pH about 3.5 (strongly acidic).

What kind of onions grow in Ruby, AK?

Long-day onions: the longest day near 99768 is 22 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99768 change?

Yes. The 2012 USDA map put 99768 in zone 2a; the 2023 map puts it in zone 3a. The newer map uses 1991–2020 data and more weather stations.