Ismay, Montana, sits in USDA hardiness zone 4a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, cranberry, turkish rocket, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Ismay, 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 Ismay 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 Ismay — soil, climate, flood, and parcel records. How we handle your address.
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Ismay — the short answer
Ismay, Montana: USDA zone 4a, about 152 days between hard freezes, across 269 acres of town.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~152
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 269 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 4a is Ismay's average, not your lot's — a low corner or a tree line moves it. Against Ismay's 152-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Ismay
Each reading below is measured for Ismay itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredIsmay runs about 152 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
MeasuredIsmay sits in USDA hardiness zone 4a.
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 Ismay is in
Ismay sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. That is read at Ismay's own centroid rather than borrowed from Custer County.
What Grows in Ismay
Every plant below cleared Ismay's own zone 4a and its 152-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Ismay?
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 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 3 — 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 Ismay
Closest first, within ~10 miles of Ismay. Listing isn't leaking, and distance isn't exposure.
- 08N55E25AA 01Nitrate · 5.1 mi
- 09N56E36ABB 01Nitrate · 8.4 mi
Measured from Ismay'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 Ismay.
Severity Distribution
within ~10 miles of Ismay
Know Before You Grow
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Ismay
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 Ismay average
Your land is one point inside Ismay
Everything above resolves to Ismay as a whole — one PHZM band and one 28°F frost record, read across 269 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 Ismay Average
Ismay Average
- ●USDA Zones 4a, averaged across Ismay
- ●One soil character for all of Ismay
- ●Frost dates read at Ismay's scale: May 4 to Oct 3
YOUR Parcel
- ✓Your exact zone, not Ismay's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Ismay
Pull a site-specific report for your exact address in Ismay, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Ismay averages can't show:
We read public map data around Ismay — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Ismay average
How we know this about Ismay
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 Ismay’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 Ismay
When does frost risk typically end in Ismay?
The last hard freeze (28°F) in Ismay typically lands around May 4, 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 25.
When is the first frost in Ismay?
The first hard freeze (28°F) in Ismay typically arrives around Oct 3, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 19, so the watching starts about Sep 3 — about 152 days after the spring freeze cleared.
How long is the growing season in Ismay?
Measured between 28°F hard freezes, Ismay sees about 152 frost-free days — roughly May 4 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 19, about 117 days.
Is the soil safe to grow vegetables in Ismay?
The federal record around Ismay is light — 4 documented sites across the 9 federal source types we checked, mostly Nitrate entries (4), the nearest Nitrate record about 5.1 miles out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Ismay?
From about Sep 3 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 3 (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 3. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Ismay's scale — its 4a band and its 152-day season. Your yard writes its own version of Ismay'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 Ismay’s own scale
6 of the readings below were taken at Ismay's own scale — its own ~152-day season between 28°F freezes, the 269 acres it covers and 4 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Ismay's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Ismay's own 28°F hard-freeze dates, about May 4 and Oct 3 and the ~152-day span between themNOAA 1991–2020 Climate Normals
- 4 documented contamination sites on the federal record near Ismay, the closest Nitrate record about 5.1 miles out from the town centreFederal environmental registers
- Ismay's boundary and the 269 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~152-day seasonGrowable Ground crop-matching engine
- The ecoregion at Ismay's own centroid, the Northwestern Great PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Ismay's 269 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 Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
- 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 Ismay's 269 acreswhy one lot differs from the next →
- Which side of Ismay you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 269 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 5.1 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 Ismay-wide figureread your own land →
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