Iona, Idaho, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Iona, 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 Iona 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 Iona — soil, climate, flood, and parcel records. How we handle your address.
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Iona — the short answer
Iona, Idaho: USDA zone 5b, about 154 days between hard freezes, across 826 acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 5
- 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
- ~154
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 826 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 Iona's average, not your lot's — a low corner or a tree line moves it. Against Iona's 154-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Iona
Each reading below is measured for Iona itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredIona runs about 154 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
MeasuredIona 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 Iona is in
Iona sits in the Snake River Plain — EPA Level III, inside the wider North American Deserts. That is read at Iona's own centroid, and it is not what its county reads: Bonneville County is mostly Middle Rockies. The wider page above you is answering a different question about different ground.
What Grows in Iona
Every plant below cleared Iona's own zone 5b and its 154-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Iona?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 5 (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. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
What's on the federal record near Iona
Closest first, within ~10 miles of Iona. Listing isn't leaking, and distance isn't exposure.
- IONA BUTTE RSUnderground Storage Tanks · 150 ft
- ROCKWOOD GARAGEUnderground Storage Tanks · 500 ft
- 02N 38E 01DAC1Nitrate · 900 ft
- G & C DISTRIBUTINGUnderground Storage Tanks · 2100 ft
- 6-12 EZ MARTUnderground Storage Tanks · 0.5 mi
- NEAHL H JOHNSONUnderground Storage Tanks · 0.8 mi
- IDAHO BONDED, INC. J.R. SUnderground Storage Tanks · 1.6 mi
- BONNEVILLE JOINT SCHOOL DIST 93Underground Storage Tanks · 1.6 mi
- UNION PACIFIC RAILROAD (6)Underground Storage Tanks · 1.8 mi
- RAIN FOR RENTUnderground Storage Tanks · 1.8 mi
- IDAHO DEPARTMENT OF LANDS (5)Underground Storage Tanks · 1.8 mi
- 02N 39E 18ADA1Nitrate · 1.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Iona'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 Iona.
Total Sites
527
within ~10 miles of Iona
Risk Level
Elevated
Highest-severity
15 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Iona
Severity Distribution
within ~10 miles of Iona
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Iona, Underground Storage Tanks runs higher than the national average — 372 sites within ~10 miles of Iona. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Iona
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 Iona average
Your land is one point inside Iona
Everything above resolves to Iona as a whole — one PHZM band and one 28°F frost record, read across 826 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 Iona Average
Iona Average
- ●USDA Zones 5b, averaged across Iona
- ●One soil character for all of Iona
- ●Frost dates read at Iona's scale: May 5 to Oct 6
YOUR Parcel
- ✓Your exact zone, not Iona's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Iona
Pull a site-specific report for your exact address in Iona, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Iona averages can't show:
We read public map data around Iona — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iona average
How we know this about Iona
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 Iona’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 Iona
When does frost risk typically end in Iona?
The last hard freeze (28°F) in Iona typically lands around May 5, 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 26.
When is the first frost in Iona?
The first hard freeze (28°F) in Iona 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 154 days after the spring freeze cleared.
How long is the growing season in Iona?
Measured between 28°F hard freezes, Iona sees about 154 frost-free days — roughly May 5 through Oct 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 26 to Sep 22, about 119 days.
Is the soil safe to grow vegetables in Iona?
The federal record around Iona is a meaningful one — 527 documented sites, mostly Underground Storage Tanks entries (372), the nearest Underground Storage Tanks record under a tenth of a mile 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 Iona?
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 Iona's scale — its 5b band and its 154-day season. Your yard writes its own version of Iona'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 Iona’s own scale
6 of the readings below were taken at Iona's own scale — its own ~154-day season between 28°F freezes, the 826 acres it covers and 527 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Iona's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Iona's own 28°F hard-freeze dates, about May 5 and Oct 6 and the ~154-day span between themNOAA 1991–2020 Climate Normals
- 527 documented contamination sites on the federal record near Iona, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Iona's boundary and the 826 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~154-day seasonGrowable Ground crop-matching engine
- Iona sits in the Snake River Plain — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Iona's 826 acres read through its county's SSURGO summaryfrom Bonneville County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Bonneville 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 Bonneville County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Iona's 826 acreswhy one lot differs from the next →
- Which side of Iona you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 826 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 Iona-wide figureread your own land →
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