Arco, Idaho, sits in USDA hardiness zones 5a-6b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Growers here do well with potato, apple, hop, and cherry — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Arco, 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 Arco lot. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Quick Facts
USDA Zones
5a-6b
Last Hard Freeze (28°F)
Apr 28
Town normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Oct 11
Town normal — light frosts arrive a few weeks earlier
City Area
684 acres
Hardiness Zone Range
Zone maps are averages across Arco. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil varies lot by lot — soil types explained.
What Grows in Arco
Plants matched to Arco's USDA zones 5a-6b — each links to its full growing profile.
Is it too late to plant in Arco?
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 11 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Growing Challenges in Idaho
What an experienced grower plans around here — each one has a move.
Short growing season at higher elevations
At elevation, fast varieties plus a cold frame or low tunnel reliably buy back the weeks the calendar withholds.
Arid conditions require irrigation in most of the state
Drip irrigation and deep mulch are the arid-country baseline — set the water system before the plants.
Cold winter snaps can reach -30F in mountain valleys
Plant perennials for your real zone, not an optimistic one — a -30°F night finds every zone-pushed plant.
For cultivar selection, pest pressure, and planting-time guidance specific to Idaho, the University of Idaho Extension is the authoritative local source.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Severity Distribution
within ~10 miles of Arco
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Arco, Nitrate runs higher than the national average — 46 sites nearby. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Arco
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Your Specific Parcel Matters
Arco Average
- ●USDA Zones 5a-6b
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Arco
Pull a site-specific report for your exact address in Arco, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for Arco, Idaho
- USDA Hardiness Zones: 5a-6b (USDA PHZM 2023)
- Last Hard Freeze (28°F): Apr 28 (town normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Oct 11 (town normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~166 (town normal, NOAA 1991–2020 Climate Normals)
- Land Area: 684 acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. Boundaries: US Census TIGER/Line 2025.
Frequently Asked Questions
What hardiness zone is Arco, Idaho?
Arco sits in USDA hardiness zones 5a-6b, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Arco?
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 11 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
When does frost risk typically end in Arco?
The last hard freeze (28°F) in Arco typically lands around Apr 28, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
When is the first frost in Arco?
The first hard freeze (28°F) in Arco typically arrives around Oct 11, per NOAA 1991–2020 climate normals — the point most tender summer crops finish. Lighter frosts usually reach a couple of weeks earlier, so watch the forecast from late summer on and harvest or cover tender plants before the first cold night.
What vegetables grow in Arco?
Arco's zones 5a-6b support a wide range — strong performers include Potato, Apple, Hop, Cherry, and Lentil. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Arco, really?
Officially, Arco sits in USDA zones 5a-6b (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Arco?
The federal record around Arco shows 74 documented sites — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Arco?
As the season closes around the first 28°F hard freeze near Oct 11 (NOAA 1991–2020 climate normals), a few moves buy time: cover tender plants with floating row cover or an old sheet on still, clear nights, water the soil the afternoon before a freeze so it holds warmth overnight, and harvest frost-tender crops like tomatoes, peppers, and basil before the first hard night. Hardy greens and root crops shrug off light frost and often sweeten after it, so leave them in.
Everything on this page is a Arco average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
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