The Inland Northwest (Northeast Washington) spans USDA hardiness zones 6a-6b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
The coldest, most continental corner of Washington. Spokane sits at USDA zone 6b, and the Colville and Selkirk highlands of Ferry and Pend Oreille counties drop to 6a — two to three zones colder than the state's maritime west side. Frost-free windows run just 167 to 202 days here, so the growing calendar leans on cold-hardy varieties, a later last-frost start, and a shorter tomato-and-pepper season than anywhere else mapped in Washington. This is NOAA's Northeastern Washington climate division (#9) — hot, dry summers and cold-snap winters across Spokane, Colville, Republic, and Newport. Well-matched crops include garlic, kale, potato, and apple, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
The Inland Northwest (Northeast Washington) spans Washington.
Your yard isn't all of the Inland Northwest (Northeast Washington).
The Inland Northwest (Northeast Washington) spans USDA zones 6a-6b, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Inland Northwest (Northeast Washington) — soil, climate, flood, and parcel records. How we handle your address.
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The Inland Northwest (Northeast Washington) — the short answer
The Inland Northwest (Northeast Washington): USDA zones 6a-6b, 167–202 frost-free days depending where in it you stand, in Washington.
- USDA zones
- 6a-6b
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 167 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Ferry County
- Counties
- 4
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. The season figure is this region's own record, measured across its 4 member counties, not a state or national average.
Hardiness Zone Range
The Inland Northwest (Northeast Washington) is not one growing season
One answer for the Inland Northwest (Northeast Washington) averages 4 counties whose growing seasons are 35 days apart — from 167 frost-free days in Ferry County to 202 in Spokane County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 4 counties runs 167–182 days, with a median of 171 days — a 35-day span end to end.
Measured across 4 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
What Grows in the Inland Northwest (Northeast Washington)
Plants matched to the Inland Northwest (Northeast Washington)'s USDA zones 6a-6b, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Inland Northwest (Northeast Washington)
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Inland Northwest (Northeast Washington)’s USDA zones 6a-6b — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Inland Northwest (Northeast Washington)
The USDA soil survey maps this ground county by county. These are those records weighted by land area across four member counties — this region’s own profile, not a state figure.
The ground is predominantly Inceptisols, at 37% of mapped acres, followed by Mollisols (29%), Andisols (24%) and Alfisols (6%). Eight soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Aits, Newbell, and Nevine.
82% of those acres are well drained, and another 5% moderately well drained, 4% somewhat excessively drained. Topsoil pH runs 6.2–6.7 between the lowest and the highest county on record. 6% of the footprint is classed prime farmland.
Soil order
Inceptisols
Drainage
Well drained
Topsoil pH
6.2–6.7
Hydric soils
2%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Spokane County holds the most wetland ground here, at 5% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Inland Northwest (Northeast Washington)
The soil survey reads this ground county by county, and the readings above are those records summed across the Inland Northwest (Northeast Washington). Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records82% of the mapped acres across the Inland Northwest (Northeast Washington) are well drained — ground that drains quickly. That is area-weighted across all four of its mapped counties.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Inland Northwest (Northeast Washington) runs pH 6.2–6.7 — near neutral in all four of them.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the Inland Northwest (Northeast Washington) — and how to grow with it.
Across the Inland Northwest (Northeast Washington)'s 4 counties the federal record holds 4,314 documented sites, mostly Mining (1,448), Underground Storage Tanks (1,431) and Nitrate (888). The heaviest single county is Spokane County, with 2,118.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Inland Northwest (Northeast Washington) to see which records sit where you actually grow.
Sources Checked
Summed across the 4 counties in the Inland Northwest (Northeast Washington)
A note from Gnorman
What an experienced grower watches for around here
In and around the Inland Northwest (Northeast Washington), Mining runs higher than the national average — 1,448 sites across the 4 counties in the Inland Northwest (Northeast Washington). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Inland Northwest (Northeast Washington)
Everything above resolves to the Inland Northwest (Northeast Washington) as a whole — a footprint whose own counties record seasons 35 days apart, and hardiness across zones 6a-6b. Your parcel sits at one point in that range, not in the middle of it. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at region scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better regional average.
Your Lot vs the Inland Northwest (Northeast Washington) Average
Inland Northwest (Northeast Washington) Average
- ●USDA Zones 6a-6b, averaged across Inland Northwest (Northeast Washington)
- ●One soil character for all of Inland Northwest (Northeast Washington)
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Inland Northwest (Northeast Washington)'s 6a-6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Inland Northwest (Northeast Washington)
Pull a site-specific report for your exact address in the Inland Northwest (Northeast Washington) — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Inland Northwest (Northeast Washington) averages can't show:
We read public map data around The Inland Northwest (Northeast Washington) — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Inland Northwest (Northeast Washington) average
How we know this about the Inland Northwest (Northeast Washington)
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Inland Northwest (Northeast Washington)
What hardiness zone is the Inland Northwest (Northeast Washington)?
The Inland Northwest (Northeast Washington) spans USDA hardiness zones 6a-6b, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Inland Northwest (Northeast Washington)?
Measured between 28°F hard freezes, the Inland Northwest (Northeast Washington)'s counties mostly run 167 to 182 frost-free days, median 171 (NOAA Regional Climate Centers ACIS, 1991–2020, over 4 member counties). That 15-day spread is the honest read — no single season describes 4 counties, and each county guide below carries its own.
When does frost risk end in the Inland Northwest (Northeast Washington)?
Across the Inland Northwest (Northeast Washington), the middle half of member counties see their last 28°F hard freeze between Apr 18 and Apr 30 (median Apr 25), and their first fall freeze between Oct 13 and Oct 18. Those are hard freezes, not the last light frost: tender transplants wait for about May 16, and elevation decides which end of a 12-day spread you garden in.
What grows well in the Inland Northwest (Northeast Washington)?
The Inland Northwest (Northeast Washington)'s conditions suit plants such as Garlic, Kale, Potato, Apple, Cherry, Hop. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Inland Northwest (Northeast Washington) defined?
The Inland Northwest (Northeast Washington) is defined here as a curated cluster of 4 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Inland Northwest (Northeast Washington) cover?
The Inland Northwest (Northeast Washington) spans Washington. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Pacific Northwest, Columbia Basin, Puget Sound Lowlands, Columbia Gorge, Olympic Peninsula, and Olympic Rain Shadow share at least one state with the Inland Northwest (Northeast Washington). Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Inland Northwest (Northeast Washington)’s own scale
6 of the readings below were taken at the Inland Northwest (Northeast Washington)'s own scale — the zone 6a-6b band across its footprint, a median 171-day season across its 4 counties and 4,314 documented federal contamination records across its 4 counties, 2,118 of them in Spokane County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 6a-6b aggregated across all 4 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 4 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 4 counties run 167 to 182 frost-free days, median 171NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 4,314 documented federal contamination records across its 4 counties, 2,118 of them in Spokane County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 37% Inceptisols, topsoil pH 6.2–6.7, area-weighted across its 4 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 6a-6bfrom Washington
What this page can’t tell you
- Which end of the 15-day range your ground sits at — 167 days at one extreme, 182 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Inland Northwest (Northeast Washington)
State growing guides
Counties in this region
Other growing regions across Washington
The maritime Northwest west of the Cascade crest — mild, wet winters and dry summers behind berries, tree fruit, and lush cool-season gardens. (Union of the west-side ecoregions.)
A dry basalt plateau of loess soils in the inland Northwest where irrigation turns arid ground into apple, cherry, hop, and wine-grape country.
The maritime lowland ringing Puget Sound — EPA's Puget Lowland ecoregion across Island, Kitsap, Mason, San Juan, and Thurston counties — where mild marine winters hold USDA zones 8a-9a and a long 227-to-300-day frost-free season.
A river canyon cut through the Cascades where wet marine air gives way to high desert in forty miles — pear, cherry, and apple orchards at the west end, vineyards and dryland ground at the east.
The Olympic Peninsula grows in a maritime world of its own. Cooled and watered by the open Pacific and the Strait of Juan de Fuca, its four counties — Clallam, Jefferson, Grays Harbor, and Mason — hold one of the widest rainfall gradients in the contiguous U.S.: from the Hoh and Quinault temperate rainforests (140+ inches a year) to the Sequim–Dungeness rain shadow near 16 inches that made the valley North America's lavender country. Long, mild, cloud-tempered seasons (USDA zones 8a–8b) favor cool-season crops — brassicas, alliums, salad greens, hardy berries, and cider apples — over heat-lovers, and frost timing swings sharply as you climb from tidewater toward the Olympic Mountains (which is why Jefferson County reads a full zone cooler and shorter-seasoned than its coastal neighbors). This page reads the peninsula's own counties, not a Pacific-Northwest-wide average, so the season and zone figures reflect the coast you're actually standing on.
Tucked in the Olympics' dry lee, Sequim and the island towns see a fraction of the rain that soaks the rest of western Washington — sunny, mild 8b-9a garden country where lavender thrives and irrigation, not drainage, is the summer question.