Mount Carroll, Illinois, sits in USDA hardiness zone 5a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Crops well matched to these conditions include cabbage, cranberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Mount Carroll, 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 Mount Carroll 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 Mount Carroll — soil, climate, flood, and parcel records. How we handle your address.
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Mount Carroll — the short answer
Mount Carroll, Illinois: USDA zone 5a, about 177 days between hard freezes, across 1K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 21
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~177
- 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 5a is Mount Carroll's average, not your lot's — a low corner or a tree line moves it. Against Mount Carroll's 177-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mount Carroll
Each reading below is measured for Mount Carroll itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMount Carroll runs about 177 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
MeasuredMount Carroll sits in USDA hardiness zone 5a.
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 Mount Carroll is in
Mount Carroll sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Mount Carroll's own centroid rather than borrowed from Carroll County.
What Grows in Mount Carroll
Every plant below cleared Mount Carroll's own zone 5a and its 177-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Mount Carroll?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 15 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Mount Carroll
Closest first, within ~10 miles of Mount Carroll. Listing isn't leaking, and distance isn't exposure.
- Mount Carroll MobilUnderground Storage Tanks · 250 ft
- Union 76 ServUnderground Storage Tanks · 350 ft
- Carroll Co Hwy DeptUnderground Storage Tanks · 1000 ft
- Ctr Hill SchoolUnderground Storage Tanks · 1000 ft
- Mount Carroll School Dist #304Underground Storage Tanks · 1400 ft
- Mount Carroll Sewer DeptUnderground Storage Tanks · 1600 ft
- Carroll CountyUnderground Storage Tanks · 2300 ft
- Street DeptUnderground Storage Tanks · 0.5 mi
- Amstar PetroleumUnderground Storage Tanks · 0.6 mi
- NORTHWEST BODY COBrownfields · 0.7 mi
- Bee Line SerUnderground Storage Tanks · 0.7 mi
- METFORM LLCToxics Release Inventory · 0.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mount Carroll'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 Mount Carroll.
Total Sites
94
within ~10 miles of Mount Carroll
Risk Level
Moderate
Highest-severity
8 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Mount Carroll
Severity Distribution
within ~10 miles of Mount Carroll
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mount Carroll, two things run higher than the national average within ~10 miles of Mount Carroll — CAFO (9 sites) and Toxics Release Inventory (8 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Mount Carroll
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 Mount Carroll average
Your land is one point inside Mount Carroll
Everything above resolves to Mount Carroll 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 Mount Carroll Average
Mount Carroll Average
- ●USDA Zones 5a, averaged across Mount Carroll
- ●One soil character for all of Mount Carroll
- ●Frost dates read at Mount Carroll's scale: Apr 21 to Oct 15
YOUR Parcel
- ✓Your exact zone, not Mount Carroll's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mount Carroll
Pull a site-specific report for your exact address in Mount Carroll, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mount Carroll averages can't show:
We read public map data around Mount Carroll — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mount Carroll average
How we know this about Mount Carroll
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 Mount Carroll’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 Mount Carroll
When does frost risk typically end in Mount Carroll?
The last hard freeze (28°F) in Mount Carroll typically lands around Apr 21, 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 12.
When is the first frost in Mount Carroll?
The first hard freeze (28°F) in Mount Carroll typically arrives around Oct 15, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 1, so the watching starts about Sep 15 — about 177 days after the spring freeze cleared.
How long is the growing season in Mount Carroll?
Measured between 28°F hard freezes, Mount Carroll sees about 177 frost-free days — roughly Apr 21 through Oct 15, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 12 to Oct 1, about 142 days.
Is the soil safe to grow vegetables in Mount Carroll?
The federal record around Mount Carroll shows 94 documented sites, mostly Underground Storage Tanks entries (54), 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 Mount Carroll?
From about Sep 15 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 15 (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 15. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Mount Carroll's scale — its 5a band and its 177-day season. Your yard writes its own version of Mount Carroll'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 Mount Carroll’s own scale
6 of the readings below were taken at Mount Carroll's own scale — its own ~177-day season between 28°F freezes, the 1,282 acres it covers and 94 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Mount Carroll's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Mount Carroll's own 28°F hard-freeze dates, about Apr 21 and Oct 15 and the ~177-day span between themNOAA 1991–2020 Climate Normals
- 94 documented contamination sites on the federal record near Mount Carroll, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Mount Carroll's boundary and the 1,282 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~177-day seasonGrowable Ground crop-matching engine
- The ecoregion at Mount Carroll's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Mount Carroll's 1,282 acres read through its county's SSURGO summaryfrom Carroll County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Carroll County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Carroll County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mount Carroll's 1,282 acreswhy one lot differs from the next →
- Which side of Mount Carroll you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,282 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 Mount Carroll-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisMount Carroll sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides