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

Planting zone for 99180 — Usk, WA

ZIP code 99180 (Usk, Pend Oreille County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 12 and the first fall frost September 21.

Where ZIP 99180 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostMay 12

First frostSep 21

2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Usk, 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 Usk, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 12median — 50% chance of a later frost

Safe for tender plantsMay 29only 10% chance of frost after

First fall frostSeptember 21median — 10% chance by Sep 5

Growing season130 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 2.

From the NOAA station Newport, WA — 14 miles away, elevation 2,162 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 99180

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 31 – Apr 14

SpinachSow outdoors · Mar 31 – Apr 21

Broccoli, cabbageStart indoors · Mar 3 – Mar 17

Broccoli, cabbageTransplant · Apr 21 – May 5

Onion setsPlant outdoors · Apr 14 – Apr 28

PotatoesPlant outdoors · Apr 21 – May 5

LettuceSow outdoors · Apr 14 – Apr 28

Carrots, beetsSow outdoors · Apr 21 – May 5

TomatoesStart indoors · Mar 17 – Mar 31

TomatoesTransplant · May 19 – Jun 2

Peppers, eggplantStart indoors · Mar 3 – Mar 17

Peppers, eggplantTransplant · May 26 – Jun 9

BeansSow outdoors · May 19 – Jun 2

Sweet cornSow outdoors · May 19 – Jun 2

Cucumbers, squashSow outdoors · May 19 – Jun 2

Fall lettuce, spinachSow outdoors · Jul 27 – Aug 10

GarlicPlant cloves · Sep 7 – Oct 12

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 12) and first fall frost (Sep 21) 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 99180 came on Apr 4 — 8 days earlier than the 1991–2020 average (Apr 12).

average
Apr 122026
Apr 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 6a in Washington

576 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 6a. 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 Usk, WA.

Soil in Usk, WA

The soil mapped at the center of ZIP 99180 is Cusick — silty clay loam, somewhat poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

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

DrainageSomewhat poorly drainedconsider raised beds

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Cusick silty clay 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 99180; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Usk, WA

Summer high84 °Faverage high, July

Winter low23 °Faverage low, February

Hot days21days a year at 90 °F or more

Freezing nights169nights a year at 32 °F or less

Growing degree days1,824base 50 °F — the season’s usable heat

Longest day16 h 06 mindaylight on June 21

Shortest day8 h 19 mindaylight on December 21

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

Precipitation27.5 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: Newport, WA (14 mi away); precipitation: Newport, WA (14 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Loon Lake, WA · 18 mi

838566a

Priest River, ID · 19 mi

990096b

Elk, WA · 19 mi

838046b

Blanchard, ID · 24 mi

Washington planting zones →

Questions about 99180

What planting zone is ZIP code 99180?

ZIP code 99180 (Usk, WA) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Usk, WA?

The median last spring frost (32 °F) near 99180 is May 12; after May 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Newport station.

When is the first frost in Usk, WA?

The median first fall frost near 99180 is September 21, giving a median frost-free growing season of 130 days.

When should I plant tomatoes in 99180?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 99180 get?

About 27.5 inches of precipitation a year (NOAA 1991–2020 normals, Newport station).

How hot do summers get in Usk, WA?

The average high peaks at 84 °F in July, with about 21 days a year at 90 °F or more.

What kind of soil does 99180 have?

The USDA soil survey maps Cusick at the center of ZIP 99180: silty clay loam, somewhat poorly drained, pH about 6.1 (slightly acidic).

Did spring come early in Usk, WA in 2026?

Spring leaf-out near 99180 came on Apr 4 in 2026, 8 days earlier than the 1991–2020 average (Apr 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Usk, WA?

Long-day onions: the longest day near 99180 is 16 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).