Challis, Idaho, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Challis, 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 Challis 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 Challis — soil, climate, flood, and parcel records. How we handle your address.
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Challis — the short answer
Challis, Idaho: USDA zone 5b, about 156 days between hard freezes, across 1K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~156
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 1K 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 5b is Challis's average, not your lot's — a low corner or a tree line moves it. Against Challis's 156-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Challis
Each reading below is measured for Challis itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredChallis runs about 156 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
MeasuredChallis sits in USDA hardiness zone 5b.
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 Challis is in
Challis sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Challis's own centroid, and it is not what its county reads: Custer County is mostly Idaho Batholith. The wider page above you is answering a different question about different ground.
What Grows in Challis
Every plant below cleared Challis's own zone 5b and its 156-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Challis?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 6 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Challis
Closest first, within ~10 miles of Challis. Listing isn't leaking, and distance isn't exposure.
- Brett's AutomotiveUnderground Storage Tanks · 500 ft
- CHALLIS JOINT SCHOOL DISTUnderground Storage Tanks · 750 ft
- SALMON RIVER ELECTRIC CO-Underground Storage Tanks · 1200 ft
- USDA USFS R04 SALMON CHALLIS NF CHALLIS COMPOUNDBrownfields · 1400 ft
- 14N 19E 33ABBD1Nitrate · 1600 ft
- GATEWAY MINI MARTUnderground Storage Tanks · 1800 ft
- 14N 19E 28CAD1Nitrate · 2100 ft
- Stinker Store #88 Jenson OilUnderground Storage Tanks · 2100 ft
- CHALLIS AVIATIONUnderground Storage Tanks · 2300 ft
- CUSTER COUNTY GOVERNMENTUnderground Storage Tanks · 2300 ft
- THOMPSON CREEK MINING COUnderground Storage Tanks · 2300 ft
- THOMAS CREEK LANDINGUnderground Storage Tanks · 2300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Challis'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 Challis.
Sources Checked
within ~10 miles of Challis
Severity Distribution
within ~10 miles of Challis
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Challis, two things run higher than the national average within ~10 miles of Challis — Mining (30 sites) and Nitrate (24 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 Challis
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 Challis average
Your land is one point inside Challis
Everything above resolves to Challis as a whole — one PHZM band and one 28°F frost record, read across 1K 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 Challis Average
Challis Average
- ●USDA Zones 5b, averaged across Challis
- ●One soil character for all of Challis
- ●Frost dates read at Challis's scale: May 3 to Oct 6
YOUR Parcel
- ✓Your exact zone, not Challis's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Challis
Pull a site-specific report for your exact address in Challis, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Challis averages can't show:
We read public map data around Challis — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Challis average
How we know this about Challis
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 Challis’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 Challis
When does frost risk typically end in Challis?
The last hard freeze (28°F) in Challis typically lands around May 3, 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 24.
When is the first frost in Challis?
The first hard freeze (28°F) in Challis typically arrives around Oct 6, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 22, so the watching starts about Sep 6 — about 156 days after the spring freeze cleared.
How long is the growing season in Challis?
Measured between 28°F hard freezes, Challis sees about 156 frost-free days — roughly May 3 through Oct 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 24 to Sep 22, about 121 days.
Is the soil safe to grow vegetables in Challis?
The federal record around Challis runs heavier than most — 72 documented sites, mostly Mining entries (30), the nearest Underground Storage Tanks record under a tenth of a mile 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 Challis?
From about Sep 6 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 6 (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 6. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Challis's scale — its 5b band and its 156-day season. Your yard writes its own version of Challis'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 Challis’s own scale
6 of the readings below were taken at Challis's own scale — its own ~156-day season between 28°F freezes, the 1,263 acres it covers and 72 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Challis's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Challis's own 28°F hard-freeze dates, about May 3 and Oct 6 and the ~156-day span between themNOAA 1991–2020 Climate Normals
- 72 documented contamination sites on the federal record near Challis, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Challis's boundary and the 1,263 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~156-day seasonGrowable Ground crop-matching engine
- Challis sits in the Middle Rockies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Challis's 1,263 acres read through its county's SSURGO summaryfrom Custer County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Custer 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 Custer County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Challis's 1,263 acreswhy one lot differs from the next →
- Which side of Challis you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,263 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile 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 Challis-wide figureread your own land →
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