Coulee Dam, Washington, sits in USDA hardiness zone 7b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
The conditions favor cabbage, prickly pear, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Coulee Dam, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Coulee Dam lot. 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 Coulee Dam — soil, climate, flood, and parcel records. How we handle your address.
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Coulee Dam — the short answer
Coulee Dam, Washington: USDA zone 7b, about 228 days between hard freezes, across 458 acres of town.
- USDA zone
- 7b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~228
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 458 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 7b is Coulee Dam's average, not your lot's — a low corner or a tree line moves it. Against Coulee Dam's 228-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Coulee Dam
Each reading below is measured for Coulee Dam itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCoulee Dam runs about 228 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredCoulee Dam sits in USDA hardiness zone 7b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Coulee Dam is in
Coulee Dam sits in the Columbia Plateau — EPA Level III, inside the wider North American Deserts. That is read at Coulee Dam's own centroid, and it is not what its county reads: Okanogan County is mostly North Cascades. The wider page above you is answering a different question about different ground.
What Grows in Coulee Dam
Every plant below cleared Coulee Dam's own zone 7b and its 228-day season. Each card opens that plant's Washington profile. How we score.
Is it too late to plant in Coulee Dam?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Feb 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
What's on the federal record near Coulee Dam
Closest first, within ~10 miles of Coulee Dam. Listing isn't leaking, and distance isn't exposure.
- GRAND COULEE DAM SCHOOL DIST 301 JUnderground Storage Tanks · 800 ft
- Riverbank stabilization Well #DW-38Nitrate · 1500 ft
- COULEE DAM CITY OFUnderground Storage Tanks · 0.6 mi
- COULEE VIEW FOOD & FUELUnderground Storage Tanks · 0.7 mi
- GRAND COULEE DAMSuperfund · 0.8 mi
- GRAND COULEE DAMBrownfields · 0.8 mi
- BONNEVILLE POWER ADMINISTRATIONUnderground Storage Tanks · 1.4 mi
- Elmer City WellNitrate · 2.1 mi
- DAM SITE BLD CENTERUnderground Storage Tanks · 2.2 mi
- COULEE GASUnderground Storage Tanks · 2.3 mi
- SAFEWAY 3247Brownfields · 2.3 mi
- CARLSON MOTORSUnderground Storage Tanks · 2.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Coulee Dam's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Coulee Dam.
Total Sites
48
within ~10 miles of Coulee Dam
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Coulee Dam
Severity Distribution
within ~10 miles of Coulee Dam
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Coulee Dam, two things run higher than the national average within ~10 miles of Coulee Dam — Mining (7 sites) and Nitrate (16 sites). That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Coulee Dam
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Coulee Dam average
Your land is one point inside Coulee Dam
Everything above resolves to Coulee Dam as a whole — one PHZM band and one 28°F frost record, read across 458 acres. Your parcel is one point inside that footprint. 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 town 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 local average.
Your Lot vs the Coulee Dam Average
Coulee Dam Average
- ●USDA Zones 7b, averaged across Coulee Dam
- ●One soil character for all of Coulee Dam
- ●Frost dates read at Coulee Dam's scale: Mar 26 to Nov 9
YOUR Parcel
- ✓Your exact zone, not Coulee Dam's 7b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Coulee Dam
Pull a site-specific report for your exact address in Coulee Dam, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Coulee Dam averages can't show:
We read public map data around Coulee Dam — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Coulee Dam average
How we know this about Coulee Dam
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Coulee Dam’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Coulee Dam
When does frost risk typically end in Coulee Dam?
The last hard freeze (28°F) in Coulee Dam typically lands around Mar 26, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Apr 16.
When is the first frost in Coulee Dam?
The first hard freeze (28°F) in Coulee Dam typically arrives around Nov 9, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 26, so the watching starts about Oct 10 — about 228 days after the spring freeze cleared.
How long is the growing season in Coulee Dam?
Measured between 28°F hard freezes, Coulee Dam sees about 228 frost-free days — roughly Mar 26 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 16 to Oct 26, about 193 days.
Is the soil safe to grow vegetables in Coulee Dam?
The federal record around Coulee Dam is a meaningful one — 48 documented sites, mostly Underground Storage Tanks entries (19), the nearest Underground Storage Tanks record about 0.1 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Coulee Dam?
From about Oct 10 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Nov 9 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Nov 9. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Coulee Dam's scale — its 7b band and its 228-day season. Your yard writes its own version of Coulee Dam's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Coulee Dam’s own scale
6 of the readings below were taken at Coulee Dam's own scale — its own ~228-day season between 28°F freezes, the 458 acres it covers and 48 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Coulee Dam's own USDA hardiness band, zones 7bUSDA PHZM 2023
- Coulee Dam's own 28°F hard-freeze dates, about Mar 26 and Nov 9 and the ~228-day span between themNOAA 1991–2020 Climate Normals
- 48 documented contamination sites on the federal record near Coulee Dam, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Coulee Dam's boundary and the 458 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7b and a ~228-day seasonGrowable Ground crop-matching engine
- Coulee Dam sits in the Columbia Plateau — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Coulee Dam's 458 acres read through its county's SSURGO summaryfrom Okanogan County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Okanogan County
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Okanogan County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Coulee Dam's 458 acreswhy one lot differs from the next →
- Which side of Coulee Dam you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 458 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Coulee Dam-wide figureread your own land →