Hillsboro, Illinois, sits in USDA hardiness zone 6b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Expect cabbage, hazelnut, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Hillsboro, 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 Hillsboro 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 Hillsboro — soil, climate, flood, and parcel records. How we handle your address.
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Hillsboro — the short answer
Hillsboro, Illinois: USDA zone 6b, about 221 days between hard freezes, across 6K acres of city.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 30
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~221
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 6K 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 6b is Hillsboro's average, not your lot's — a low corner or a tree line moves it. Against Hillsboro's 221-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hillsboro
Each reading below is measured for Hillsboro itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHillsboro runs about 221 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredHillsboro sits in USDA hardiness zone 6b.
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 Hillsboro is in
Hillsboro sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Hillsboro's own centroid rather than borrowed from Montgomery County.
What Grows in Hillsboro
Every plant below cleared Hillsboro's own zone 6b and its 221-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Hillsboro?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 2; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 30 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 6 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
What's on the federal record near Hillsboro
Closest first, within ~10 miles of Hillsboro. Listing isn't leaking, and distance isn't exposure.
- 9N 3W-31.4aNitrate · 1800 ft
- EAGLE ZINC COBrownfields · 0.7 mi
- EAGLE ZINC COToxics Release Inventory · 0.7 mi
- Eagle Zinc CompanyUnderground Storage Tanks · 0.9 mi
- MONTGOMERY CO HOUSING AUTHBrownfields · 1.0 mi
- Schram City Village OfUnderground Storage Tanks · 1.0 mi
- EAGLE ZINC COSuperfund · 1.1 mi
- Hillsboro StationUnderground Storage Tanks · 1.1 mi
- LIVINGSTON PIPE & TUBE INCBrownfields · 1.2 mi
- HILLSBORO GLASS COToxics Release Inventory · 1.2 mi
- Hillsboro Glass CoUnderground Storage Tanks · 1.2 mi
- Fil-T-Kleen Co IncUnderground Storage Tanks · 1.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Hillsboro'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 Hillsboro.
Sources Checked
within ~10 miles of Hillsboro
Severity Distribution
within ~10 miles of Hillsboro
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hillsboro, two things run higher than the national average within ~10 miles of Hillsboro — CAFO (3 sites) and Superfund (3 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.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Hillsboro
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 Hillsboro average
Your land is one point inside Hillsboro
Everything above resolves to Hillsboro as a whole — one PHZM band and one 28°F frost record, read across 6K 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 Hillsboro Average
Hillsboro Average
- ●USDA Zones 6b, averaged across Hillsboro
- ●One soil character for all of Hillsboro
- ●Frost dates read at Hillsboro's scale: Mar 30 to Nov 6
YOUR Parcel
- ✓Your exact zone, not Hillsboro's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hillsboro
Pull a site-specific report for your exact address in Hillsboro, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hillsboro averages can't show:
We read public map data around Hillsboro — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hillsboro average
How we know this about Hillsboro
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 Hillsboro’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 Hillsboro
When does frost risk typically end in Hillsboro?
The last hard freeze (28°F) in Hillsboro typically lands around Mar 30, 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 Apr 20.
When is the first frost in Hillsboro?
The first hard freeze (28°F) in Hillsboro typically arrives around Nov 6, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 23, so the watching starts about Oct 7 — about 221 days after the spring freeze cleared.
How long is the growing season in Hillsboro?
Measured between 28°F hard freezes, Hillsboro sees about 221 frost-free days — roughly Mar 30 through Nov 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 20 to Oct 23, about 186 days.
Is the soil safe to grow vegetables in Hillsboro?
The federal record around Hillsboro is a meaningful one — 130 documented sites, mostly Underground Storage Tanks entries (83), the nearest Nitrate record about 0.3 miles 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 Hillsboro?
From about Oct 7 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 Nov 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 Nov 6. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hillsboro's scale — its 6b band and its 221-day season. Your yard writes its own version of Hillsboro'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 Hillsboro’s own scale
6 of the readings below were taken at Hillsboro's own scale — its own ~221-day season between 28°F freezes, the 5,590 acres it covers and 130 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Hillsboro's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Hillsboro's own 28°F hard-freeze dates, about Mar 30 and Nov 6 and the ~221-day span between themNOAA 1991–2020 Climate Normals
- 130 documented contamination sites on the federal record near Hillsboro, the closest Nitrate record about 0.3 miles out from the town centreFederal environmental registers
- Hillsboro's boundary and the 5,590 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~221-day seasonGrowable Ground crop-matching engine
- The ecoregion at Hillsboro's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Hillsboro's 5,590 acres read through its county's SSURGO summaryfrom Montgomery County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Montgomery 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 Montgomery County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hillsboro's 5,590 acreswhy one lot differs from the next →
- Which side of Hillsboro you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,590 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.3 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 Hillsboro-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisHillsboro sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides