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

Planting zone for 98537 — Cosmopolis, WA

ZIP code 98537 (Cosmopolis, Grays Harbor County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 26 and the first fall frost October 17.

Where ZIP 98537 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 26
First frostOct 17
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 Cosmopolis, 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 Cosmopolis, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 26median — 50% chance of a later frost
Safe for tender plantsMay 12only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 1
Growing season177 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 27 and returns around November 7.

From the NOAA station Raymond 2 S, WA — 13 miles away, elevation 30 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 98537

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 15 – Mar 29
SpinachSow outdoors · Mar 15 – Apr 5
Broccoli, cabbageStart indoors · Feb 15 – Mar 1
Broccoli, cabbageTransplant · Apr 5 – Apr 19
Onion setsPlant outdoors · Mar 29 – Apr 12
PotatoesPlant outdoors · Apr 5 – Apr 19
LettuceSow outdoors · Mar 29 – Apr 12
Carrots, beetsSow outdoors · Apr 5 – Apr 19
TomatoesStart indoors · Mar 1 – Mar 15
TomatoesTransplant · May 3 – May 17
Peppers, eggplantStart indoors · Feb 15 – Mar 1
Peppers, eggplantTransplant · May 10 – May 24
BeansSow outdoors · May 3 – May 17
Sweet cornSow outdoors · May 3 – May 17
Cucumbers, squashSow outdoors · May 3 – May 17
Fall lettuce, spinachSow outdoors · Aug 22 – Sep 5
GarlicPlant cloves · Oct 3 – Nov 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 17) 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 98537 came on Feb 22 — 9 days earlier than the 1991–2020 average (Mar 3).

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.

Trees 32

Alaska cedar75 ft · blooms mid spring · low shade tolerance · to −22 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fbigleaf maple60 ft · blooms mid spring · medium shade tolerance · to −14 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °F

Shrubs 114

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FBarclay's willow15 ft · high shade tolerance · to −43 °F

Wildflowers & perennials 293

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 157

Alaska brome5 ft · blooms late spring · low shade tolerance · to −18 °FAlaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °F

Vines 3

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

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 Cosmopolis, WA.

Soil in Cosmopolis, WA

The soil mapped at the center of ZIP 98537 is Zenker — medial silt loam, well drained.

TextureMedial silt loama good balance for most vegetables
pH4.8strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter12.5%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Zenker silt loam, 30 to 65 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 98537; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cosmopolis, WA

Summer high73 °Faverage high, August
Winter low32 °Faverage low, February
Hot days3days a year at 90 °F or more
Freezing nights82nights a year at 32 °F or less
Growing degree days1,397base 50 °F — the season’s usable heat
Longest day15 h 52 mindaylight on June 21
Shortest day8 h 32 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation83.7 inper year, rain and melted snow
Snowfall1 inper year

Average high and low, by month

20°30°40°50°60°70°80°32 °FJanuary: average high 48 °F, low 33 °F 48°33° JanFebruary: average high 51 °F, low 32 °F 51°32° FebMarch: average high 54 °F, low 35 °F 54°35° MarApril: average high 58 °F, low 37 °F 58°37° AprMay: average high 63 °F, low 43 °F 63°43° MayJune: average high 67 °F, low 47 °F 67°47° JunJuly: average high 71 °F, low 51 °F 71°51° JulAugust: average high 73 °F, low 50 °F 73°50° AugSeptember: average high 70 °F, low 46 °F 70°46° SepOctober: average high 61 °F, low 40 °F 61°40° OctNovember: average high 52 °F, low 35 °F 52°35° NovDecember: average high 47 °F, low 32 °F 47°32° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″10″12″14″January: 13.05 in precipitation, 0.5 in snowfall 13.1❄1 JanFebruary: 8.70 in precipitation, 0.1 in snowfall 8.7 FebMarch: 9.74 in precipitation 9.7 MarApril: 6.54 in precipitation 6.5 AprMay: 3.64 in precipitation 3.6 MayJune: 2.61 in precipitation 2.6 JunJuly: 0.91 in precipitation 0.9 JulAugust: 1.36 in precipitation 1.4 AugSeptember: 3.11 in precipitation 3.1 SepOctober: 8.33 in precipitation 8.3 OctNovember: 13.02 in precipitation 13.0 NovDecember: 12.64 in precipitation, 0.5 in snowfall 12.6❄1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Raymond 2 S, WA (13 mi away); precipitation: Raymond 2 S, WA (13 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.

985778a
Raymond, WA · 12 mi
985618b
Menlo, WA · 13 mi
985688a
Oakville, WA · 14 mi
985838b
Satsop, WA · 14 mi
985598b
Malone, WA · 16 mi
985548b
Lebam, WA · 17 mi
985208b
Aberdeen, WA · 17 mi
985398a
Doty, WA · 19 mi

Washington planting zones →

Questions about 98537

What planting zone is ZIP code 98537?

ZIP code 98537 (Cosmopolis, 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 Cosmopolis, WA?

The median last spring frost (32 °F) near 98537 is April 26; after May 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Raymond 2 S station.

When is the first frost in Cosmopolis, WA?

The median first fall frost near 98537 is October 17, giving a median frost-free growing season of 177 days.

When should I plant tomatoes in 98537?

Start tomato seeds indoors around Mar 1 – Mar 15 and set transplants outside around May 3 – May 17, one to three weeks after the median last frost.

How much rain and snow does 98537 get?

About 83.7 inches of precipitation a year and 1 inches of snowfall (NOAA 1991–2020 normals, Raymond 2 S station).

How hot do summers get in Cosmopolis, WA?

The average high peaks at 73 °F in August, with about 3 days a year at 90 °F or more.

What kind of soil does 98537 have?

The USDA soil survey maps Zenker at the center of ZIP 98537: medial silt loam, well drained, pH about 4.8 (strongly acidic).

Did spring come early in Cosmopolis, WA in 2026?

Spring leaf-out near 98537 came on Feb 22 in 2026, 9 days earlier than the 1991–2020 average (Mar 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cosmopolis, WA?

Long-day onions: the longest day near 98537 is 15 h 52 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).