Circle, Montana, sits in USDA hardiness zone 4a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Crops well matched to these conditions include cabbage, cranberry, turkish rocket, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Circle, 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 Circle 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 Circle — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Circle — the short answer
Circle, Montana: USDA zone 4a, about 153 days between hard freezes, across 499 acres of town.
- USDA zone
- 4a
- 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 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~153
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 499 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 Circle's average, not your lot's — a low corner or a tree line moves it. Against Circle's 153-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Circle
Each reading below is measured for Circle itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCircle runs about 153 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
MeasuredCircle 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 Circle is in
Circle sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. That is read at Circle's own centroid rather than borrowed from McCone County.
What Grows in Circle
Every plant below cleared Circle's own zone 4a and its 153-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Circle?
Usually not — gardeners here simply switch what goes in the ground as the season moves. 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 3 — 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 Circle
Closest first, within ~10 miles of Circle. Listing isn't leaking, and distance isn't exposure.
- CIRCLE EXXONUnderground Storage Tanks · 250 ft
- HALES DISTRIBUTINGUnderground Storage Tanks · 300 ft
- FARMERS UNION OIL CO CIRCLEUnderground Storage Tanks · 500 ft
- CIRCLE COUNTRY MARKET LLCUnderground Storage Tanks · 600 ft
- CIRCLE HIGH SCHOOL SHOPBrownfields · 800 ft
- CHS NUTRITION - CIRCLEToxics Release Inventory · 1200 ft
- MID RIVERS TELEPHONE COOPUnderground Storage Tanks · 1800 ft
- FARMERS ELEVATOR CO CIRCLEUnderground Storage Tanks · 1800 ft
- MOOS FARM INCUnderground Storage Tanks · 1800 ft
- MCCONE COUNTY HOSPITALUnderground Storage Tanks · 1800 ft
- MCCONE COUNTY AIRPORTUnderground Storage Tanks · 1800 ft
- MYRON L GACKLEUnderground Storage Tanks · 1800 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Circle'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 Circle.
Total Sites
68
within ~10 miles of Circle
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Circle
Severity Distribution
within ~10 miles of Circle
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Circle, Nitrate runs higher than the national average — 48 sites within ~10 miles of Circle. That's not a problem with your land — it's information about it.
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 Circle
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 Circle average
Your land is one point inside Circle
Everything above resolves to Circle as a whole — one PHZM band and one 28°F frost record, read across 499 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 Circle Average
Circle Average
- ●USDA Zones 4a, averaged across Circle
- ●One soil character for all of Circle
- ●Frost dates read at Circle's scale: May 3 to Oct 3
YOUR Parcel
- ✓Your exact zone, not Circle's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Circle
Pull a site-specific report for your exact address in Circle, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Circle averages can't show:
We read public map data around Circle — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Circle average
How we know this about Circle
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 Circle’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 Circle
When does frost risk typically end in Circle?
The last hard freeze (28°F) in Circle 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 Circle?
The first hard freeze (28°F) in Circle 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 153 days after the spring freeze cleared.
How long is the growing season in Circle?
Measured between 28°F hard freezes, Circle sees about 153 frost-free days — roughly May 3 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 24 to Sep 19, about 118 days.
Is the soil safe to grow vegetables in Circle?
The federal record around Circle shows 68 documented sites, mostly Nitrate entries (48), the nearest Underground Storage Tanks record under a tenth of a mile out — 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 Circle?
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 Circle's scale — its 4a band and its 153-day season. Your yard writes its own version of Circle'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 Circle’s own scale
6 of the readings below were taken at Circle's own scale — its own ~153-day season between 28°F freezes, the 499 acres it covers and 68 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Circle's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Circle's own 28°F hard-freeze dates, about May 3 and Oct 3 and the ~153-day span between themNOAA 1991–2020 Climate Normals
- 68 documented contamination sites on the federal record near Circle, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Circle's boundary and the 499 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~153-day seasonGrowable Ground crop-matching engine
- The ecoregion at Circle's own centroid, the Northwestern Great PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Circle's 499 acres read through its county's SSURGO summaryfrom McCone County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom McCone 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 McCone County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Circle's 499 acreswhy one lot differs from the next →
- Which side of Circle you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 499 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 Circle-wide figureread your own land →
More in Montana
Wider growing context
What grows across MontanaCircle sits outside our named growing regions, so Montana as a whole is its closest context here.
Nearby growing guides