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

Planting zone for 98538 — Curtis, WA

ZIP code 98538 (Curtis, Lewis County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is April 5 and the first fall frost October 25.

Where ZIP 98538 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.

Zone8a10 to 15 °F

Coldest night−12.2 to −9.4 °C

Last frostApr 5

First frostOct 25

2012 zone8a

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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Curtis, 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 Curtis, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 5median — 50% chance of a later frost

Safe for tender plantsMay 4only 10% chance of frost after

First fall frostOctober 25median — 10% chance by Sep 24

Growing season196 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 10 and returns around November 9.

From the NOAA station Toledo Faa Airport, WA — 16 miles away, elevation 381 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 98538

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 22 – Mar 8

SpinachSow outdoors · Feb 22 – Mar 15

Broccoli, cabbageStart indoors · Jan 25 – Feb 8

Broccoli, cabbageTransplant · Mar 15 – Mar 29

Onion setsPlant outdoors · Mar 8 – Mar 22

PotatoesPlant outdoors · Mar 15 – Mar 29

LettuceSow outdoors · Mar 8 – Mar 22

Carrots, beetsSow outdoors · Mar 15 – Mar 29

TomatoesStart indoors · Feb 8 – Feb 22

TomatoesTransplant · Apr 12 – Apr 26

Peppers, eggplantStart indoors · Jan 25 – Feb 8

Peppers, eggplantTransplant · Apr 19 – May 3

BeansSow outdoors · Apr 12 – Apr 26

Sweet cornSow outdoors · Apr 12 – Apr 26

Cucumbers, squashSow outdoors · Apr 12 – Apr 26

Fall lettuce, spinachSow outdoors · Aug 30 – Sep 13

GarlicPlant cloves · Oct 11 – Nov 15

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 5) and first fall frost (Oct 25) 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 98538 came on Feb 28 — 5 days earlier than the 1991–2020 average (Mar 5).

average
Mar 52026
Feb 28

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 8a in Washington

611 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive 10 °F or colder — the bottom of zone 8a. 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 Curtis, WA.

Soil in Curtis, WA

The soil mapped at the center of ZIP 98538 is Katula — very cobbly loam, well drained.

TextureVery cobbly loama good balance for most vegetables

pH5.3strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter7.5%high

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Katula very cobbly loam, 65 to 90 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 98538; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Curtis, WA

Summer high81 °Faverage high, August

Winter low34 °Faverage low, February

Hot days8days a year at 90 °F or more

Freezing nights54nights a year at 32 °F or less

Growing degree days2,092base 50 °F — the season’s usable heat

Longest day15 h 49 mindaylight on June 21

Shortest day8 h 34 mindaylight on December 21

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

Precipitation54 inper year, rain and melted snow

Snowfall4 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Toledo Faa Airport, WA (16 mi away); precipitation: Doty 3 E, WA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Washington planting zones →

Questions about 98538

What planting zone is ZIP code 98538?

ZIP code 98538 (Curtis, WA) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Curtis, WA?

The median last spring frost (32 °F) near 98538 is April 5; after May 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Toledo Faa Airport station.

When is the first frost in Curtis, WA?

The median first fall frost near 98538 is October 25, giving a median frost-free growing season of 196 days.

When should I plant tomatoes in 98538?

Start tomato seeds indoors around Feb 8 – Feb 22 and set transplants outside around Apr 12 – Apr 26, one to three weeks after the median last frost.

How much rain and snow does 98538 get?

About 54 inches of precipitation a year and 4 inches of snowfall (NOAA 1991–2020 normals, Doty 3 E station).

How hot do summers get in Curtis, WA?

The average high peaks at 81 °F in August, with about 8 days a year at 90 °F or more.

What kind of soil does 98538 have?

The USDA soil survey maps Katula at the center of ZIP 98538: very cobbly loam, well drained, pH about 5.3 (strongly acidic).

Did spring come early in Curtis, WA in 2026?

Spring leaf-out near 98538 came on Feb 28 in 2026, 5 days earlier than the 1991–2020 average (Mar 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Curtis, WA?

Long-day onions: the longest day near 98538 is 15 h 49 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).