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

Planting zone for 99647 — Pedro Bay, AK

ZIP code 99647 (Pedro Bay, Lake and Peninsula County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is June 2 and the first fall frost September 12.

Where ZIP 99647 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostJun 2
First frostSep 12
2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Pedro Bay, 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 Pedro Bay, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 2median — 50% chance of a later frost
Safe for tender plantsJune 13only 10% chance of frost after
First fall frostSeptember 12median — 10% chance by Aug 29
Growing season101 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 19 and returns around September 25.

From the NOAA station Port Alsworth 1 Sw, AK — 24 miles away, elevation 322 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 99647

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 21 – May 5
SpinachSow outdoors · Apr 21 – May 12
Broccoli, cabbageStart indoors · Mar 24 – Apr 7
Broccoli, cabbageTransplant · May 12 – May 26
Onion setsPlant outdoors · May 5 – May 19
PotatoesPlant outdoors · May 12 – May 26
LettuceSow outdoors · May 5 – May 19
Carrots, beetsSow outdoors · May 12 – May 26
TomatoesStart indoors · Apr 7 – Apr 21
TomatoesTransplant · Jun 9 – Jun 23
Peppers, eggplantStart indoors · Mar 24 – Apr 7
Peppers, eggplantTransplant · Jun 16 – Jun 30
BeansSow outdoors · Jun 9 – Jun 23
Sweet cornSow outdoors · Jun 9 – Jun 23
Cucumbers, squashSow outdoors · Jun 9 – Jun 23
Fall lettuce, spinachSow outdoors · Jul 18 – Aug 1
GarlicPlant cloves · Aug 29 – Oct 3
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 2) and first fall frost (Sep 12) 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 4b in Alaska

260 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 11

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 °FPacific silver fir165 ft · blooms late spring · low shade tolerance · to −28 °Fpaper birch70 ft · blooms mid spring · high shade tolerance · to −62 °Fquaking aspen65 ft · blooms mid spring · high shade tolerance · to −70 °F

Shrubs 44

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 112

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 84

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 Pedro Bay, AK.

Soil in Pedro Bay, AK

The soil mapped at the center of ZIP 99647 is E25-Maritime tall scrub-ashy till slopes — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH4.4strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Southern Alaska Peninsula Mountains-Maritime Upland-Rounded 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 99647; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Pedro Bay, AK

Summer high67 °Faverage high, July
Winter low5 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights209nights a year at 32 °F or less
Growing degree days497base 50 °F — the season’s usable heat
Longest day18 h 49 mindaylight on June 21
Shortest day5 h 54 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation23.6 inper year, rain and melted snow

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 24 °F, low 5 °F 24°5° JanFebruary: average high 29 °F, low 10 °F 29°10° FebMarch: average high 32 °F, low 11 °F 32°11° MarApril: average high 46 °F, low 24 °F 46°24° AprMay: average high 58 °F, low 32 °F 58°32° MayJune: average high 65 °F, low 41 °F 65°41° JunJuly: average high 67 °F, low 46 °F 67°46° JulAugust: average high 63 °F, low 45 °F 63°45° AugSeptember: average high 55 °F, low 38 °F 55°38° SepOctober: average high 42 °F, low 25 °F 42°25° OctNovember: average high 30 °F, low 15 °F 30°15° NovDecember: average high 25 °F, low 9 °F 25°9° Dec

Precipitation by month inches

0″1″2″3″4″January: 1.55 in precipitation 1.6 JanFebruary: 1.48 in precipitation 1.5 FebMarch: 1.17 in precipitation 1.2 MarApril: 0.91 in precipitation 0.9 AprMay: 0.84 in precipitation 0.8 MayJune: 1.24 in precipitation 1.2 JunJuly: 2.15 in precipitation 2.1 JulAugust: 3.32 in precipitation 3.3 AugSeptember: 3.48 in precipitation 3.5 SepOctober: 2.25 in precipitation 2.3 OctNovember: 3.03 in precipitation 3.0 NovDecember: 2.17 in precipitation 2.2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Port Alsworth 1 Sw, AK (24 mi away); precipitation: Port Alsworth 1 Sw, AK (24 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

4 of the 6 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

996534a
Port Alsworth, AK · 21 mi
996064b
Iliamna, AK · 31 mi
996134a
King Salmon, AK · 72 mi
996404a
Nondalton, AK · 77 mi
996354b
Nikiski, AK · 90 mi
995573a
Aniak, AK · 116 mi

Alaska planting zones →

Questions about 99647

What planting zone is ZIP code 99647?

ZIP code 99647 (Pedro Bay, AK) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Pedro Bay, AK?

The median last spring frost (32 °F) near 99647 is June 2; after June 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Port Alsworth 1 Sw station.

When is the first frost in Pedro Bay, AK?

The median first fall frost near 99647 is September 12, giving a median frost-free growing season of 101 days.

When should I plant tomatoes in 99647?

Start tomato seeds indoors around Apr 7 – Apr 21 and set transplants outside around Jun 9 – Jun 23, one to three weeks after the median last frost.

How much rain and snow does 99647 get?

About 23.6 inches of precipitation a year (NOAA 1991–2020 normals, Port Alsworth 1 Sw station).

How hot do summers get in Pedro Bay, 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 99647 have?

The USDA soil survey maps E25-Maritime tall scrub-ashy till slopes at the center of ZIP 99647: slightly decomposed plant material, well drained, pH about 4.4 (strongly acidic).

What kind of onions grow in Pedro Bay, AK?

Long-day onions: the longest day near 99647 is 18 h 49 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99647 change?

Yes. The 2012 USDA map put 99647 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.