Clark Fork, Idaho, sits in USDA hardiness zone 6b — a zone band wide enough that plant choice, not possibility, is the interesting question.
The conditions favor cabbage, blackberry, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Clark Fork, 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 Clark Fork 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 Clark Fork — soil, climate, flood, and parcel records. How we handle your address.
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Clark Fork — the short answer
Clark Fork, Idaho: USDA zone 6b, about 167 days between hard freezes, across 630 acres of city.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~167
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 630 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 6b is Clark Fork's average, not your lot's — a low corner or a tree line moves it. Against Clark Fork's 167-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Clark Fork
Each reading below is measured for Clark Fork itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredClark Fork runs about 167 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredClark Fork sits in USDA hardiness zone 6b.
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 Clark Fork is in
Clark Fork sits in the Northern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Clark Fork's own centroid rather than borrowed from Bonner County.
What Grows in Clark Fork
Every plant below cleared Clark Fork's own zone 6b and its 167-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Clark Fork?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 31; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 12 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
What's on the federal record near Clark Fork
Closest first, within ~10 miles of Clark Fork. Listing isn't leaking, and distance isn't exposure.
- CLARK FORK BEVERAGEUnderground Storage Tanks · 1100 ft
- CLARK FORK EXXONUnderground Storage Tanks · 1100 ft
- CLARK FORK SCHOOLUnderground Storage Tanks · 1300 ft
- CLARK FORK CTRL OFC (1030-B02)Underground Storage Tanks · 1500 ft
- CX RANCH/JAMES E WHITE ESTATEUnderground Storage Tanks · 1600 ft
- BNRR - CLARK FORK MICROWAVE SITEUnderground Storage Tanks · 1600 ft
- HAYS CHEVRONUnderground Storage Tanks · 1600 ft
- Pier and CadyMining · 2200 ft
- Whitcomb LeaseMining · 2200 ft
- Lawrence MineMining · 0.6 mi
- Pier & Cady MineMining · 0.7 mi
- Little SenatorMining · 0.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Clark Fork'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 Clark Fork.
Total Sites
122
within ~10 miles of Clark Fork
Risk Level
High
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Clark Fork
Severity Distribution
within ~10 miles of Clark Fork
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Clark Fork, Mining runs higher than the national average — 82 sites within ~10 miles of Clark Fork. 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.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Clark Fork
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 Clark Fork average
Your land is one point inside Clark Fork
Everything above resolves to Clark Fork as a whole — one PHZM band and one 28°F frost record, read across 630 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 city 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 Clark Fork Average
Clark Fork Average
- ●USDA Zones 6b, averaged across Clark Fork
- ●One soil character for all of Clark Fork
- ●Frost dates read at Clark Fork's scale: Apr 28 to Oct 12
YOUR Parcel
- ✓Your exact zone, not Clark Fork's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Clark Fork
Pull a site-specific report for your exact address in Clark Fork, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Clark Fork averages can't show:
We read public map data around Clark Fork — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Clark Fork average
How we know this about Clark Fork
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Clark Fork’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 city grain anywhere on this page — there is no city-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 Clark Fork
When does frost risk typically end in Clark Fork?
The last hard freeze (28°F) in Clark Fork typically lands around Apr 28, 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 May 19.
When is the first frost in Clark Fork?
The first hard freeze (28°F) in Clark Fork typically arrives around Oct 12, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 28, so the watching starts about Sep 12 — about 167 days after the spring freeze cleared.
How long is the growing season in Clark Fork?
Measured between 28°F hard freezes, Clark Fork sees about 167 frost-free days — roughly Apr 28 through Oct 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 19 to Sep 28, about 132 days.
Is the soil safe to grow vegetables in Clark Fork?
The federal record around Clark Fork runs heavier than most — 122 documented sites, mostly Mining entries (82), the nearest Underground Storage Tanks record about 0.2 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do I protect my plants from frost in Clark Fork?
From about Sep 12 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 Oct 12 (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 Oct 12. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Clark Fork's scale — its 6b band and its 167-day season. Your yard writes its own version of Clark Fork'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 Clark Fork’s own scale
6 of the readings below were taken at Clark Fork's own scale — its own ~167-day season between 28°F freezes, the 630 acres it covers and 122 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Clark Fork's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Clark Fork's own 28°F hard-freeze dates, about Apr 28 and Oct 12 and the ~167-day span between themNOAA 1991–2020 Climate Normals
- 122 documented contamination sites on the federal record near Clark Fork, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Clark Fork's boundary and the 630 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~167-day seasonGrowable Ground crop-matching engine
- The ecoregion at Clark Fork's own centroid, the Northern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Clark Fork's 630 acres read through its county's SSURGO summaryfrom Bonner County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Bonner County
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Bonner County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Clark Fork's 630 acreswhy one lot differs from the next →
- Which side of Clark Fork you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 630 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 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 Clark Fork-wide figureread your own land →
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