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

Planting zone for 98029 — Issaquah, WA

ZIP code 98029 (Issaquah, King County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is March 30 and the first fall frost November 7.

Where ZIP 98029 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 30

First frostNov 7

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 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 — 8 miles away, 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 98029

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.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 8b.

All 2 ZIP codes in Issaquah → · Washington planting zones →

Questions about 98029

What planting zone is ZIP code 98029?

ZIP code 98029 (Issaquah, 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 Issaquah, WA?

The median last spring frost (32 °F) near 98029 is March 30; after April 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Snoqualmie Falls station.

When is the first frost in Issaquah, WA?

The median first fall frost near 98029 is November 7, giving a median frost-free growing season of 223 days.

When should I plant tomatoes in 98029?

Start tomato seeds indoors around Feb 2 – Feb 16 and set transplants outside around Apr 6 – Apr 20, one to three weeks after the median last frost.

How much rain and snow does 98029 get?

About 47.4 inches of precipitation a year (NOAA 1991–2020 normals, Issaquah 3.6 Nw station).

How hot do summers get in Issaquah, WA?

The average high peaks at 77 °F in August, with about 3 days a year at 90 °F or more.

What kind of soil does 98029 have?

The USDA soil survey maps Everett at the center of ZIP 98029: slightly decomposed plant material, somewhat excessively drained, pH about 4.5 (strongly acidic).

Did spring come early in Issaquah, WA in 2026?

Spring leaf-out near 98029 came on Feb 15 in 2026, 11 days earlier than the 1991–2020 average (Feb 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Issaquah, WA?

Long-day onions: the longest day near 98029 is 15 h 59 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).