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

Planting zone for Issaquah, WA

Issaquah, WA is in USDA zone 8b across its 2 ZIP codes. The median last spring frost is March 30 and the first fall frost November 7.

Issaquah on the zone map

Outlined: its 2 ZIP code areas · 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

ZIP codes2

Last frostMar 30

First frostNov 7

Growing season223 days

8b 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Issaquah, 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 Issaquah, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMarch 30median — 50% chance of a later frost

Safe for tender plantsApril 21only 10% chance of frost after

First fall frostNovember 7median — 10% chance by Oct 22

Growing season223 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 27 and returns around November 29.

From the NOAA station Snoqualmie Falls, WA, elevation 440 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 Issaquah

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 16 – Mar 2

SpinachSow outdoors · Feb 16 – Mar 9

Broccoli, cabbageStart indoors · Jan 19 – Feb 2

Broccoli, cabbageTransplant · Mar 9 – Mar 23

Onion setsPlant outdoors · Mar 2 – Mar 16

PotatoesPlant outdoors · Mar 9 – Mar 23

LettuceSow outdoors · Mar 2 – Mar 16

Carrots, beetsSow outdoors · Mar 9 – Mar 23

TomatoesStart indoors · Feb 2 – Feb 16

TomatoesTransplant · Apr 6 – Apr 20

Peppers, eggplantStart indoors · Jan 19 – Feb 2

Peppers, eggplantTransplant · Apr 13 – Apr 27

BeansSow outdoors · Apr 6 – Apr 20

Sweet cornSow outdoors · Apr 6 – Apr 20

Cucumbers, squashSow outdoors · Apr 6 – Apr 20

Fall lettuce, spinachSow outdoors · Sep 12 – Sep 26

GarlicPlant cloves · Oct 24 – Nov 28

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 30) and first fall frost (Nov 7) 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 98029 came on Feb 15 — 11 days earlier than the 1991–2020 average (Feb 26).

average
Feb 262026
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 Issaquah, WA.

Soil in Issaquah, WA

The soil mapped at the center of ZIP 98029 is Everett — slightly decomposed plant material, somewhat excessively drained.

TextureSlightly decomposed plant materialtop layer

pH4.5strongly acidic; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter75%high

Hydrologic groupAwater soaks in fast

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Everett very gravelly sandy loam, 15 to 30 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 98029; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Issaquah, WA

Summer high77 °Faverage high, August

Winter low35 °Faverage low, February

Hot days3days a year at 90 °F or more

Freezing nights54nights a year at 32 °F or less

Growing degree days1,889base 50 °F — the season’s usable heat

Longest day15 h 59 mindaylight on June 21

Shortest day8 h 26 mindaylight on December 21

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

Precipitation47.4 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: Snoqualmie Falls, WA (8 mi away); precipitation: Issaquah 3.6 Nw, WA (4 mi away). Daylight is calculated from latitude.

ZIP codes in Issaquah

Washington planting zones →

Questions about Issaquah

What planting zone is Issaquah, WA?

Issaquah, WA is in USDA hardiness zone 8b on the 2023 map (8b: 15 to 20 °F).

When is the last frost in Issaquah, WA?

The median last spring frost is March 30 and the median first fall frost is November 7 (NOAA 1991–2020 normals, Snoqualmie Falls station).

When can I plant a garden in Issaquah, WA?

Cool-season crops like peas and spinach go in around Feb 16 – Mar 9; tomatoes, peppers, beans and squash after about Apr 6, once frost risk has passed.

What kind of onions grow in Issaquah, WA?

Long-day onions: the longest day is 15 h 59 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Issaquah, WA get?

About 47.4 inches of precipitation a year (NOAA 1991–2020 normals).