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

Planting zone for 98278 — Oak Harbor, WA

ZIP code 98278 (Oak Harbor, Island County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is March 13 and the first fall frost November 14.

Where ZIP 98278 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.

Zone8b15 to 20 °F

Coldest night−9.4 to −6.7 °C

Last frostMar 13

First frostNov 14

2012 zone8b

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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Oak Harbor, WA…

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 Oak Harbor, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

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

Safe for tender plantsApril 1only 10% chance of frost after

First fall frostNovember 14median — 10% chance by Oct 26

Growing season244 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 18 and returns around December 1.

From the NOAA station Whidbey Island NAS, WA — within 1 mile, elevation 46 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 98278

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 30 – Feb 13

SpinachSow outdoors · Jan 30 – Feb 20

Broccoli, cabbageStart indoors · Jan 2 – Jan 16

Broccoli, cabbageTransplant · Feb 20 – Mar 6

Onion setsPlant outdoors · Feb 13 – Feb 27

PotatoesPlant outdoors · Feb 20 – Mar 6

LettuceSow outdoors · Feb 13 – Feb 27

Carrots, beetsSow outdoors · Feb 20 – Mar 6

TomatoesStart indoors · Jan 16 – Jan 30

TomatoesTransplant · Mar 20 – Apr 3

Peppers, eggplantStart indoors · Jan 2 – Jan 16

Peppers, eggplantTransplant · Mar 27 – Apr 10

BeansSow outdoors · Mar 20 – Apr 3

Sweet cornSow outdoors · Mar 20 – Apr 3

Cucumbers, squashSow outdoors · Mar 20 – Apr 3

Fall lettuce, spinachSow outdoors · Sep 19 – Oct 3

GarlicPlant cloves · Oct 31 – Dec 5

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 13) and first fall frost (Nov 14) 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.

When spring arrived in 2026

In 2026, spring leaf-out near 98278 came on Feb 15 — about the same time as the 1991–2020 average (Feb 16).

average
Feb 162026
Feb 15

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 8b in Washington

614 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive 15 °F or colder — the bottom of zone 8b. 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 Oak Harbor, WA.

Soil in Oak Harbor, WA

The soil mapped at the center of ZIP 98278 is Coveland — loam, somewhat poorly drained.

TextureLoama good balance for most vegetables

pH6.4slightly acidic; most vegetables like 6.0–7.0

DrainageSomewhat poorly drainedconsider raised beds

Organic matter9%high

Hydrologic groupC/Dslow when drained; wet otherwise

Farmland classPrime farmland if drainedUSDA classification

Map unit: Coveland loam, cool, 0 to 5 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 98278; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Oak Harbor, WA

Summer high70 °Faverage high, August

Winter low37 °Faverage low, February

Hot days0days a year at 90 °F or more

Freezing nights40nights a year at 32 °F or less

Growing degree days1,664base 50 °F — the season’s usable heat

Longest day16 h 06 mindaylight on June 21

Shortest day8 h 19 mindaylight on December 21

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

Precipitation19.9 inper year, rain and melted snow

Snowfall5 inper year; 3 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: Whidbey Island NAS, WA (within 1 mile); precipitation: Whidbey Island NAS, WA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

982778b

Oak Harbor, WA · 3 mi

Coupeville, WA · 10 mi

982828b

Camano Island, WA · 12 mi

982619a

Lopez Island, WA · 14 mi

982738b

Mount Vernon, WA · 14 mi

982388b

Conway, WA · 15 mi

All 2 ZIP codes in Oak Harbor → · Washington planting zones →

Questions about 98278

What planting zone is ZIP code 98278?

ZIP code 98278 (Oak Harbor, WA) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Oak Harbor, WA?

The median last spring frost (32 °F) near 98278 is March 13; after April 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Whidbey Island NAS station.

When is the first frost in Oak Harbor, WA?

The median first fall frost near 98278 is November 14, giving a median frost-free growing season of 244 days.

When should I plant tomatoes in 98278?

Start tomato seeds indoors around Jan 16 – Jan 30 and set transplants outside around Mar 20 – Apr 3, one to three weeks after the median last frost.

How much rain and snow does 98278 get?

About 19.9 inches of precipitation a year and 5 inches of snowfall (NOAA 1991–2020 normals, Whidbey Island NAS station).

How hot do summers get in Oak Harbor, WA?

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

What kind of soil does 98278 have?

The USDA soil survey maps Coveland at the center of ZIP 98278: loam, somewhat poorly drained, pH about 6.4 (slightly acidic).

Did spring come early in Oak Harbor, WA in 2026?

Spring leaf-out near 98278 came on Feb 15 in 2026, about the same as the 1991–2020 average (Feb 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Oak Harbor, WA?

Long-day onions: the longest day near 98278 is 16 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).