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

Planting zone for 98237 — Concrete, WA

ZIP code 98237 (Concrete, Skagit County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is March 28 and the first fall frost November 14.

Where ZIP 98237 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 frostMar 28
First frostNov 14
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 Concrete, 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 Concrete, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 28median — 50% chance of a later frost
Safe for tender plantsApril 19only 10% chance of frost after
First fall frostNovember 14median — 10% chance by Oct 23
Growing season229 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 25 and returns around December 2.

From the NOAA station Concrete Ppl Fish Stn, WA — within 1 mile, elevation 194 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 98237

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 14 – Feb 28
SpinachSow outdoors · Feb 14 – Mar 7
Broccoli, cabbageStart indoors · Jan 17 – Jan 31
Broccoli, cabbageTransplant · Mar 7 – Mar 21
Onion setsPlant outdoors · Feb 28 – Mar 14
PotatoesPlant outdoors · Mar 7 – Mar 21
LettuceSow outdoors · Feb 28 – Mar 14
Carrots, beetsSow outdoors · Mar 7 – Mar 21
TomatoesStart indoors · Jan 31 – Feb 14
TomatoesTransplant · Apr 4 – Apr 18
Peppers, eggplantStart indoors · Jan 17 – Jan 31
Peppers, eggplantTransplant · Apr 11 – Apr 25
BeansSow outdoors · Apr 4 – Apr 18
Sweet cornSow outdoors · Apr 4 – Apr 18
Cucumbers, squashSow outdoors · Apr 4 – Apr 18
Fall lettuce, spinachSow outdoors · Sep 19 – Oct 3
GarlicPlant cloves · Oct 31 – Dec 5
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 28) and first fall frost (Nov 14) 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 98237 came on Mar 18 — 11 days earlier than the 1991–2020 average (Mar 29).

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.

Trees 31

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 113

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 292

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 Concrete, WA.

Soil in Concrete, WA

The soil mapped at the center of ZIP 98237 is Barneston — 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 classPrime farmland if irrigatedUSDA classification

Map unit: Barneston gravelly ashy loam, 0 to 8 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 98237; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Concrete, WA

Summer high77 °Faverage high, August
Winter low33 °Faverage low, January
Hot days3days a year at 90 °F or more
Freezing nights47nights a year at 32 °F or less
Growing degree days1,850base 50 °F — the season’s usable heat
Longest day16 h 08 mindaylight on June 21
Shortest day8 h 17 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation71.2 inper year, rain and melted snow
Snowfall16 inper year; 15 days with snow on the ground

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 43 °F, low 33 °F 43°33° JanFebruary: average high 47 °F, low 34 °F 47°34° FebMarch: average high 52 °F, low 36 °F 52°36° MarApril: average high 58 °F, low 40 °F 58°40° AprMay: average high 65 °F, low 45 °F 65°45° MayJune: average high 69 °F, low 50 °F 69°50° JunJuly: average high 76 °F, low 53 °F 76°53° JulAugust: average high 77 °F, low 54 °F 77°54° AugSeptember: average high 71 °F, low 50 °F 71°50° SepOctober: average high 59 °F, low 44 °F 59°44° OctNovember: average high 49 °F, low 38 °F 49°38° NovDecember: average high 42 °F, low 34 °F 42°34° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″10″12″January: 10.38 in precipitation, 5 in snowfall 10.4❄5 JanFebruary: 6.72 in precipitation, 1.5 in snowfall 6.7❄2 FebMarch: 7.63 in precipitation, 1.3 in snowfall 7.6❄1 MarApril: 5.09 in precipitation 5.1 AprMay: 3.47 in precipitation 3.5 MayJune: 2.68 in precipitation 2.7 JunJuly: 1.21 in precipitation 1.2 JulAugust: 1.53 in precipitation 1.5 AugSeptember: 3.31 in precipitation 3.3 SepOctober: 7.31 in precipitation 7.3 OctNovember: 11.49 in precipitation, 0.9 in snowfall 11.5❄1 NovDecember: 10.42 in precipitation, 7.6 in snowfall 10.4❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Concrete Ppl Fish Stn, WA (within 1 mile); precipitation: Concrete Ppl Fish Stn, WA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

982558b
Hamilton, WA · 13 mi
982638b
Lyman, WA · 16 mi
982448a
Deming, WA · 19 mi
982848b
Sedro Woolley, WA · 19 mi
982677a
Marblemount, WA · 23 mi
982748b
Mount Vernon, WA · 24 mi
982358b
Clearlake, WA · 24 mi
982208a
Acme, WA · 24 mi

Washington planting zones →

Questions about 98237

What planting zone is ZIP code 98237?

ZIP code 98237 (Concrete, 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 Concrete, WA?

The median last spring frost (32 °F) near 98237 is March 28; after April 19 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Concrete Ppl Fish Stn station.

When is the first frost in Concrete, WA?

The median first fall frost near 98237 is November 14, giving a median frost-free growing season of 229 days.

When should I plant tomatoes in 98237?

Start tomato seeds indoors around Jan 31 – Feb 14 and set transplants outside around Apr 4 – Apr 18, one to three weeks after the median last frost.

How much rain and snow does 98237 get?

About 71.2 inches of precipitation a year and 16 inches of snowfall (NOAA 1991–2020 normals, Concrete Ppl Fish Stn station).

How hot do summers get in Concrete, 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 98237 have?

The USDA soil survey maps Barneston at the center of ZIP 98237: slightly decomposed plant material, somewhat excessively drained, pH about 4.5 (strongly acidic).

Did spring come early in Concrete, WA in 2026?

Spring leaf-out near 98237 came on Mar 18 in 2026, 11 days earlier than the 1991–2020 average (Mar 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Concrete, WA?

Long-day onions: the longest day near 98237 is 16 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).