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

Planting zone for 99109 — Chewelah, WA

ZIP code 99109 (Chewelah, Stevens County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 16 and the first fall frost September 15.

Where ZIP 99109 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 16
First frostSep 15
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 Chewelah, 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 Chewelah, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 16median — 50% chance of a later frost
Safe for tender plantsJune 7only 10% chance of frost after
First fall frostSeptember 15median — 10% chance by Sep 1
Growing season120 daysfrost-free, median

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

From the NOAA station Chewelah, WA — 2 miles away, elevation 1,670 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 99109

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 4 – Apr 18
SpinachSow outdoors · Apr 4 – Apr 25
Broccoli, cabbageStart indoors · Mar 7 – Mar 21
Broccoli, cabbageTransplant · Apr 25 – May 9
Onion setsPlant outdoors · Apr 18 – May 2
PotatoesPlant outdoors · Apr 25 – May 9
LettuceSow outdoors · Apr 18 – May 2
Carrots, beetsSow outdoors · Apr 25 – May 9
TomatoesStart indoors · Mar 21 – Apr 4
TomatoesTransplant · May 23 – Jun 6
Peppers, eggplantStart indoors · Mar 7 – Mar 21
Peppers, eggplantTransplant · May 30 – Jun 13
BeansSow outdoors · May 23 – Jun 6
Sweet cornSow outdoors · May 23 – Jun 6
Cucumbers, squashSow outdoors · May 23 – Jun 6
Fall lettuce, spinachSow outdoors · Jul 21 – Aug 4
GarlicPlant cloves · Sep 1 – Oct 6
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 16) and first fall frost (Sep 15) 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 99109 came on Apr 2 — 5 days earlier than the 1991–2020 average (Apr 7).

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.

Trees 30

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 102

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 276

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 153

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 Chewelah, WA.

Soil in Chewelah, WA

The soil mapped at the center of ZIP 99109 is Aits — ashy loam, well drained.

TextureAshy loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3.5%moderate
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Aits loam, 15 to 25 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 99109; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Chewelah, WA

Summer high86 °Faverage high, July
Winter low20 °Faverage low, January
Hot days34days a year at 90 °F or more
Freezing nights170nights a year at 32 °F or less
Growing degree days1,864base 50 °F — the season’s usable heat
Longest day16 h 05 mindaylight on June 21
Shortest day8 h 20 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation21.4 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 33 °F, low 20 °F 33°20° JanFebruary: average high 40 °F, low 21 °F 40°21° FebMarch: average high 50 °F, low 27 °F 50°27° MarApril: average high 60 °F, low 33 °F 60°33° AprMay: average high 70 °F, low 40 °F 70°40° MayJune: average high 76 °F, low 46 °F 76°46° JunJuly: average high 86 °F, low 49 °F 86°49° JulAugust: average high 86 °F, low 47 °F 86°47° AugSeptember: average high 76 °F, low 39 °F 76°39° SepOctober: average high 59 °F, low 31 °F 59°31° OctNovember: average high 42 °F, low 26 °F 42°26° NovDecember: average high 33 °F, low 21 °F 33°21° Dec

Precipitation by month inches

0″1″2″3″January: 2.22 in precipitation 2.2 JanFebruary: 1.85 in precipitation 1.9 FebMarch: 2.21 in precipitation 2.2 MarApril: 1.86 in precipitation 1.9 AprMay: 2.03 in precipitation 2.0 MayJune: 2.05 in precipitation 2.0 JunJuly: 0.99 in precipitation 1.0 JulAugust: 0.72 in precipitation 0.7 AugSeptember: 0.95 in precipitation 0.9 SepOctober: 1.78 in precipitation 1.8 OctNovember: 2.37 in precipitation 2.4 NovDecember: 2.33 in precipitation 2.3 Dec

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

991816b
Valley, WA · 11 mi
991016b
Addy, WA · 11 mi
991486a
Loon Lake, WA · 14 mi
991806a
Usk, WA · 18 mi
991736b
Springdale, WA · 19 mi
991106a
Clayton, WA · 20 mi
991196a
Cusick, WA · 23 mi
991146a
Colville, WA · 25 mi

Washington planting zones →

Questions about 99109

What planting zone is ZIP code 99109?

ZIP code 99109 (Chewelah, 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 Chewelah, WA?

The median last spring frost (32 °F) near 99109 is May 16; after June 7 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Chewelah station.

When is the first frost in Chewelah, WA?

The median first fall frost near 99109 is September 15, giving a median frost-free growing season of 120 days.

When should I plant tomatoes in 99109?

Start tomato seeds indoors around Mar 21 – Apr 4 and set transplants outside around May 23 – Jun 6, one to three weeks after the median last frost.

How much rain and snow does 99109 get?

About 21.4 inches of precipitation a year (NOAA 1991–2020 normals, Chewelah station).

How hot do summers get in Chewelah, WA?

The average high peaks at 86 °F in July, with about 34 days a year at 90 °F or more.

What kind of soil does 99109 have?

The USDA soil survey maps Aits at the center of ZIP 99109: ashy loam, well drained, pH about 6.7 (neutral).

Did spring come early in Chewelah, WA in 2026?

Spring leaf-out near 99109 came on Apr 2 in 2026, 5 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Chewelah, WA?

Long-day onions: the longest day near 99109 is 16 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).