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

Planting zone for 99603 — Homer, AK

ZIP code 99603 (Homer, Kenai Peninsula County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 10 and the first fall frost September 29.

Where ZIP 99603 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 10
First frostSep 29
2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Homer, 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 Homer, AK

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 10median — 50% chance of a later frost
Safe for tender plantsMay 23only 10% chance of frost after
First fall frostSeptember 29median — 10% chance by Sep 14
Growing season141 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 23 and returns around October 11.

From the NOAA station Homer Airport, AK — 13 miles away, elevation 66 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 99603

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 29 – Apr 12
SpinachSow outdoors · Mar 29 – Apr 19
Broccoli, cabbageStart indoors · Mar 1 – Mar 15
Broccoli, cabbageTransplant · Apr 19 – May 3
Onion setsPlant outdoors · Apr 12 – Apr 26
PotatoesPlant outdoors · Apr 19 – May 3
LettuceSow outdoors · Apr 12 – Apr 26
Carrots, beetsSow outdoors · Apr 19 – May 3
TomatoesStart indoors · Mar 15 – Mar 29
TomatoesTransplant · May 17 – May 31
Peppers, eggplantStart indoors · Mar 1 – Mar 15
Peppers, eggplantTransplant · May 24 – Jun 7
BeansSow outdoors · May 17 – May 31
Sweet cornSow outdoors · May 17 – May 31
Cucumbers, squashSow outdoors · May 17 – May 31
Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18
GarlicPlant cloves · Sep 15 – Oct 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Sep 29) 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 6a in Alaska

285 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 49

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 123

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 88

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 Homer, AK.

Soil in Homer, AK

The soil mapped at the center of ZIP 99603 is E20-maritime forest-loamy colluvial slopes, shallow — moderately decomposed plant material, moderately well drained.

TextureModerately decomposed plant materialtop layer
pH5.5moderately acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter75%high
Hydrologic groupCwater soaks in slowly

Map unit: Alexander Archipelago-Gulf of Alaska Coast-Maritime Upland 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 99603; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Homer, AK

Summer high63 °Faverage high, July
Winter low19 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights169nights a year at 32 °F or less
Growing degree days501base 50 °F — the season’s usable heat
Longest day18 h 42 mindaylight on June 21
Shortest day6 h 01 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation23.9 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°32 °FJanuary: average high 32 °F, low 19 °F 32°19° JanFebruary: average high 35 °F, low 22 °F 35°22° FebMarch: average high 37 °F, low 23 °F 37°23° MarApril: average high 46 °F, low 31 °F 46°31° AprMay: average high 54 °F, low 38 °F 54°38° MayJune: average high 59 °F, low 45 °F 59°45° JunJuly: average high 63 °F, low 49 °F 63°49° JulAugust: average high 63 °F, low 48 °F 63°48° AugSeptember: average high 57 °F, low 42 °F 57°42° SepOctober: average high 47 °F, low 33 °F 47°33° OctNovember: average high 38 °F, low 25 °F 38°25° NovDecember: average high 34 °F, low 21 °F 34°21° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.15 in precipitation 2.1 JanFebruary: 1.82 in precipitation 1.8 FebMarch: 1.32 in precipitation 1.3 MarApril: 1.15 in precipitation 1.1 AprMay: 0.78 in precipitation 0.8 MayJune: 0.87 in precipitation 0.9 JunJuly: 1.45 in precipitation 1.4 JulAugust: 2.31 in precipitation 2.3 AugSeptember: 3.28 in precipitation 3.3 SepOctober: 2.61 in precipitation 2.6 OctNovember: 2.87 in precipitation 2.9 NovDecember: 3.27 in precipitation 3.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Homer Airport, AK (13 mi away); precipitation: Homer Airport, AK (13 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

7 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

996636b
Seldovia, AK · 18 mi
995566a
Anchor Point, AK · 25 mi
996395b
Ninilchik, AK · 33 mi
996104b
Kasilof, AK · 51 mi
995685a
Clam Gulch, AK · 55 mi
996694b
Soldotna, AK · 57 mi
996724b
Sterling, AK · 73 mi
995725a
Cooper Landing, AK · 81 mi

Alaska planting zones →

Questions about 99603

What planting zone is ZIP code 99603?

ZIP code 99603 (Homer, AK) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Homer, AK?

The median last spring frost (32 °F) near 99603 is May 10; after May 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Homer Airport station.

When is the first frost in Homer, AK?

The median first fall frost near 99603 is September 29, giving a median frost-free growing season of 141 days.

When should I plant tomatoes in 99603?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 99603 get?

About 23.9 inches of precipitation a year (NOAA 1991–2020 normals, Homer Airport station).

How hot do summers get in Homer, AK?

The average high peaks at 63 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 99603 have?

The USDA soil survey maps E20-maritime forest-loamy colluvial slopes, shallow at the center of ZIP 99603: moderately decomposed plant material, moderately well drained, pH about 5.5 (moderately acidic).

What kind of onions grow in Homer, AK?

Long-day onions: the longest day near 99603 is 18 h 42 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).