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

Planting zone for 99611 — Kenai, AK

ZIP code 99611 (Kenai, Kenai Peninsula County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is June 1 and the first fall frost September 8.

Where ZIP 99611 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.

Zone5a−20 to −15 °F

Coldest night−28.9 to −26.1 °C

Last frostJun 1

First frostSep 8

2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Kenai, 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 Kenai, AK

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 1median — 50% chance of a later frost

Safe for tender plantsJune 18only 10% chance of frost after

First fall frostSeptember 8median — 10% chance by Aug 21

Growing season94 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 14 and returns around September 21.

From the NOAA station Kenai 29 Ene, AK — 12 miles away, elevation 282 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 99611

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 20 – May 4

SpinachSow outdoors · Apr 20 – May 11

Broccoli, cabbageStart indoors · Mar 23 – Apr 6

Broccoli, cabbageTransplant · May 11 – May 25

Onion setsPlant outdoors · May 4 – May 18

PotatoesPlant outdoors · May 11 – May 25

LettuceSow outdoors · May 4 – May 18

Carrots, beetsSow outdoors · May 11 – May 25

TomatoesStart indoors · Apr 6 – Apr 20

TomatoesTransplant · Jun 8 – Jun 22

Peppers, eggplantStart indoors · Mar 23 – Apr 6

Peppers, eggplantTransplant · Jun 15 – Jun 29

BeansSow outdoors · Jun 8 – Jun 22

Sweet cornSow outdoors · Jun 8 – Jun 22

Cucumbers, squashSow outdoors · Jun 8 – Jun 22

Fall lettuce, spinachSow outdoors · Jul 14 – Jul 28

GarlicPlant cloves · Aug 25 – Sep 29

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 1) and first fall frost (Sep 8) 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 5a in Alaska

275 plants native to Alaska, recorded in Alaska, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. 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 Kenai, AK.

Soil in Kenai, AK

The soil mapped at the center of ZIP 99611 is Starichkof — peat, very poorly drained.

TexturePeattop layer

pH4.3strongly acidic; most vegetables like 6.0–7.0

DrainageVery poorly drainedconsider raised beds

Organic matter90%high

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Starichkof-Slikok-Naptowne complex, 0 to 15 percent slopes.

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 99611; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kenai, AK

Summer high67 °Faverage high, July

Winter low3 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights219nights a year at 32 °F or less

Growing degree days447base 50 °F — the season’s usable heat

Longest day19 h 12 mindaylight on June 21

Shortest day5 h 35 mindaylight on December 21

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

Precipitation18.6 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kenai 29 Ene, AK (12 mi away); precipitation: Kenai Moose Pens, AK (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Anchorage, AK · 33 mi

995725a

Cooper Landing, AK · 34 mi

995155a

Anchorage, AK · 34 mi

995295b

Anchorage, AK · 34 mi

996694b

Soldotna, AK · 34 mi

995305b

Anchorage, AK · 35 mi

Alaska planting zones →

Questions about 99611

What planting zone is ZIP code 99611?

ZIP code 99611 (Kenai, AK) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Kenai, AK?

The median last spring frost (32 °F) near 99611 is June 1; after June 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kenai 29 Ene station.

When is the first frost in Kenai, AK?

The median first fall frost near 99611 is September 8, giving a median frost-free growing season of 94 days.

When should I plant tomatoes in 99611?

Start tomato seeds indoors around Apr 6 – Apr 20 and set transplants outside around Jun 8 – Jun 22, one to three weeks after the median last frost.

How much rain and snow does 99611 get?

About 18.6 inches of precipitation a year (NOAA 1991–2020 normals, Kenai Moose Pens station).

How hot do summers get in Kenai, 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 99611 have?

The USDA soil survey maps Starichkof at the center of ZIP 99611: peat, very poorly drained, pH about 4.3 (strongly acidic).

What kind of onions grow in Kenai, AK?

Long-day onions: the longest day near 99611 is 19 h 12 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99611 change?

Yes. The 2012 USDA map put 99611 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.