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

Planting zone for 98626 — Kelso, WA

ZIP code 98626 (Kelso, Cowlitz County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 8 and the first fall frost November 5.

Where ZIP 98626 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 frostApr 8

First frostNov 5

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 Kelso, 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 Kelso, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 8median — 50% chance of a later frost

Safe for tender plantsMay 2only 10% chance of frost after

First fall frostNovember 5median — 10% chance by Oct 17

Growing season210 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 6 and returns around November 24.

From the NOAA station Longview, WA — 7 miles away, elevation 13 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 98626

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 25 – Mar 11

SpinachSow outdoors · Feb 25 – Mar 18

Broccoli, cabbageStart indoors · Jan 28 – Feb 11

Broccoli, cabbageTransplant · Mar 18 – Apr 1

Onion setsPlant outdoors · Mar 11 – Mar 25

PotatoesPlant outdoors · Mar 18 – Apr 1

LettuceSow outdoors · Mar 11 – Mar 25

Carrots, beetsSow outdoors · Mar 18 – Apr 1

TomatoesStart indoors · Feb 11 – Feb 25

TomatoesTransplant · Apr 15 – Apr 29

Peppers, eggplantStart indoors · Jan 28 – Feb 11

Peppers, eggplantTransplant · Apr 22 – May 6

BeansSow outdoors · Apr 15 – Apr 29

Sweet cornSow outdoors · Apr 15 – Apr 29

Cucumbers, squashSow outdoors · Apr 15 – Apr 29

Fall lettuce, spinachSow outdoors · Sep 10 – Sep 24

GarlicPlant cloves · Oct 22 – Nov 26

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Nov 5) 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 98626 came on Feb 22 — 5 days earlier than the 1991–2020 average (Feb 27).

average
Feb 272026
Feb 22

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 Kelso, WA.

Soil in Kelso, WA

The soil mapped at the center of ZIP 98626 is Olympic — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.1slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter5.5%high

Hydrologic groupBwater soaks in moderately

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Olympic silt loam, 8 to 20 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 98626; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kelso, WA

Summer high80 °Faverage high, August

Winter low35 °Faverage low, January

Hot days10days a year at 90 °F or more

Freezing nights41nights a year at 32 °F or less

Growing degree days2,268base 50 °F — the season’s usable heat

Longest day15 h 47 mindaylight on June 21

Shortest day8 h 37 mindaylight on December 21

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

Precipitation48.1 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: Longview, WA (7 mi away); precipitation: Longview, WA (7 mi away). 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.

Castle Rock, WA · 11 mi

986458b

Silverlake, WA · 11 mi

Washington planting zones →

Questions about 98626

What planting zone is ZIP code 98626?

ZIP code 98626 (Kelso, 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 Kelso, WA?

The median last spring frost (32 °F) near 98626 is April 8; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Longview station.

When is the first frost in Kelso, WA?

The median first fall frost near 98626 is November 5, giving a median frost-free growing season of 210 days.

When should I plant tomatoes in 98626?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 98626 get?

About 48.1 inches of precipitation a year (NOAA 1991–2020 normals, Longview station).

How hot do summers get in Kelso, WA?

The average high peaks at 80 °F in August, with about 10 days a year at 90 °F or more.

What kind of soil does 98626 have?

The USDA soil survey maps Olympic at the center of ZIP 98626: silt loam, well drained, pH about 6.1 (slightly acidic).

Did spring come early in Kelso, WA in 2026?

Spring leaf-out near 98626 came on Feb 22 in 2026, 5 days earlier than the 1991–2020 average (Feb 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Kelso, WA?

Long-day onions: the longest day near 98626 is 15 h 47 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).