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

Planting zone for 98643 — Rosburg, WA

ZIP code 98643 (Rosburg, Wahkiakum County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 24 and the first fall frost October 20.

Where ZIP 98643 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 24

First frostOct 20

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 Rosburg, 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 Rosburg, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 24median — 50% chance of a later frost

Safe for tender plantsMay 11only 10% chance of frost after

First fall frostOctober 20median — 10% chance by Oct 1

Growing season179 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 19 and returns around November 6.

From the NOAA station Naselle 2 Ene, WA — 7 miles away, elevation 49 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 98643

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 13 – Mar 27

SpinachSow outdoors · Mar 13 – Apr 3

Broccoli, cabbageStart indoors · Feb 13 – Feb 27

Broccoli, cabbageTransplant · Apr 3 – Apr 17

Onion setsPlant outdoors · Mar 27 – Apr 10

PotatoesPlant outdoors · Apr 3 – Apr 17

LettuceSow outdoors · Mar 27 – Apr 10

Carrots, beetsSow outdoors · Apr 3 – Apr 17

TomatoesStart indoors · Feb 27 – Mar 13

TomatoesTransplant · May 1 – May 15

Peppers, eggplantStart indoors · Feb 13 – Feb 27

Peppers, eggplantTransplant · May 8 – May 22

BeansSow outdoors · May 1 – May 15

Sweet cornSow outdoors · May 1 – May 15

Cucumbers, squashSow outdoors · May 1 – May 15

Fall lettuce, spinachSow outdoors · Aug 25 – Sep 8

GarlicPlant cloves · Oct 6 – Nov 10

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 24) and first fall frost (Oct 20) 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 98643 came on Feb 4 — 13 days earlier than the 1991–2020 average (Feb 17).

average
Feb 172026
Feb 4

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 Rosburg, WA.

Soil in Rosburg, WA

The soil mapped at the center of ZIP 98643 is Nuby — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter7.5%high

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if drainedUSDA classification

Map unit: Nuby silt loam.

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 98643; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Rosburg, WA

Summer high74 °Faverage high, August

Winter low33 °Faverage low, February

Hot days5days a year at 90 °F or more

Freezing nights76nights a year at 32 °F or less

Growing degree days1,536base 50 °F — the season’s usable heat

Longest day15 h 48 mindaylight on June 21

Shortest day8 h 36 mindaylight on December 21

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

Precipitation97.8 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: Naselle 2 Ene, WA (7 mi away); precipitation: Grays River 0.9 Sse, WA (4 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.

986388b

Naselle, WA · 9 mi

986218b

Grays River, WA · 9 mi

971038b

Astoria, OR · 11 mi

986478b

Skamokawa, WA · 12 mi

Warrenton, OR · 17 mi

Washington planting zones →

Questions about 98643

What planting zone is ZIP code 98643?

ZIP code 98643 (Rosburg, 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 Rosburg, WA?

The median last spring frost (32 °F) near 98643 is April 24; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Naselle 2 Ene station.

When is the first frost in Rosburg, WA?

The median first fall frost near 98643 is October 20, giving a median frost-free growing season of 179 days.

When should I plant tomatoes in 98643?

Start tomato seeds indoors around Feb 27 – Mar 13 and set transplants outside around May 1 – May 15, one to three weeks after the median last frost.

How much rain and snow does 98643 get?

About 97.8 inches of precipitation a year (NOAA 1991–2020 normals, Grays River 0.9 Sse station).

How hot do summers get in Rosburg, WA?

The average high peaks at 74 °F in August, with about 5 days a year at 90 °F or more.

What kind of soil does 98643 have?

The USDA soil survey maps Nuby at the center of ZIP 98643: silt loam, poorly drained, pH about 5.0 (strongly acidic).

Did spring come early in Rosburg, WA in 2026?

Spring leaf-out near 98643 came on Feb 4 in 2026, 13 days earlier than the 1991–2020 average (Feb 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Rosburg, WA?

Long-day onions: the longest day near 98643 is 15 h 48 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).