Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 99627 — Mc Grath, AK

ZIP code 99627 (Mc Grath, Yukon-Koyukuk (CA) County) is in USDA zone 2b: the coldest winter night averages −45 to −40 °F. The median last spring frost is May 13 and the first fall frost September 13.

Where ZIP 99627 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.

Zone2b−45 to −40 °F

Coldest night−42.8 to −40 °C

Last frostMay 13

First frostSep 13

2012 zone1b

Was 1b 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 2b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mc Grath, 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 Mc Grath, AK

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 13median — 50% chance of a later frost

Safe for tender plantsMay 28only 10% chance of frost after

First fall frostSeptember 13median — 10% chance by Aug 27

Growing season120 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 4 and returns around September 25.

From the NOAA station Mcgrath Airport, AK — 52 miles away, elevation 335 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 99627

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 1 – Apr 15

SpinachSow outdoors · Apr 1 – Apr 22

Broccoli, cabbageStart indoors · Mar 4 – Mar 18

Broccoli, cabbageTransplant · Apr 22 – May 6

Onion setsPlant outdoors · Apr 15 – Apr 29

PotatoesPlant outdoors · Apr 22 – May 6

LettuceSow outdoors · Apr 15 – Apr 29

Carrots, beetsSow outdoors · Apr 22 – May 6

TomatoesStart indoors · Mar 18 – Apr 1

TomatoesTransplant · May 20 – Jun 3

Peppers, eggplantStart indoors · Mar 4 – Mar 18

Peppers, eggplantTransplant · May 27 – Jun 10

BeansSow outdoors · May 20 – Jun 3

Sweet cornSow outdoors · May 20 – Jun 3

Cucumbers, squashSow outdoors · May 20 – Jun 3

Fall lettuce, spinachSow outdoors · Jul 19 – Aug 2

GarlicPlant cloves · Aug 30 – Oct 4

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 13) and first fall frost (Sep 13) 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 2b in Alaska

45 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −45 °F or colder — the bottom of zone 2b. Each links to its USDA PLANTS profile.

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 Mc Grath, AK.

Soil in Mc Grath, AK

The soil mapped at the center of ZIP 99627 is E30-boreal alpine scrub-gravelly colluvial slopes — moderately decomposed plant material, well drained.

TextureModerately decomposed plant materialtop layer

DrainageWell drainednatural drainage class

Organic matter75%high

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Yukon-Kuskokwim Highlands-Boreal Alpine and Subalpine-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 99627; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mc Grath, AK

Summer high70 °Faverage high, July

Winter low−14 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights221nights a year at 32 °F or less

Growing degree days884base 50 °F — the season’s usable heat

Longest day20 h 41 mindaylight on June 21

Shortest day4 h 26 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation18.1 inper year, rain and melted snow

Snowfall87 inper year; 191 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mcgrath Airport, AK (52 mi away); precipitation: Mcgrath Airport, AK (52 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Alaska planting zones →

Questions about 99627

What planting zone is ZIP code 99627?

ZIP code 99627 (Mc Grath, AK) is in USDA hardiness zone 2b on the 2023 map: the coldest night of an average winter reaches −45 to −40 °F (−42.8 to −40 °C).

When is the last frost in Mc Grath, AK?

The median last spring frost (32 °F) near 99627 is May 13; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mcgrath Airport station.

When is the first frost in Mc Grath, AK?

The median first fall frost near 99627 is September 13, giving a median frost-free growing season of 120 days.

When should I plant tomatoes in 99627?

Start tomato seeds indoors around Mar 18 – Apr 1 and set transplants outside around May 20 – Jun 3, one to three weeks after the median last frost.

How much rain and snow does 99627 get?

About 18.1 inches of precipitation a year and 87 inches of snowfall (NOAA 1991–2020 normals, Mcgrath Airport station).

How hot do summers get in Mc Grath, AK?

The average high peaks at 70 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99627 have?

The USDA soil survey maps E30-boreal alpine scrub-gravelly colluvial slopes at the center of ZIP 99627: moderately decomposed plant material, well drained.

What kind of onions grow in Mc Grath, AK?

Long-day onions: the longest day near 99627 is 20 h 41 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99627 change?

Yes. The 2012 USDA map put 99627 in zone 1b; the 2023 map puts it in zone 2b. The newer map uses 1991–2020 data and more weather stations.