Wilmington, Illinois, 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.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Wilmington, 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 Wilmington 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 Wilmington — soil, climate, flood, and parcel records. How we handle your address.
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Wilmington — the short answer
Wilmington, Illinois: USDA zone 5b, about 201 days between hard freezes, across 9K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~201
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 9K 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 Wilmington's average, not your lot's — a low corner or a tree line moves it. Against Wilmington's 201-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Wilmington
Each reading below is measured for Wilmington itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredWilmington runs about 201 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
MeasuredWilmington 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 Wilmington is in
Wilmington sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Wilmington's own centroid rather than borrowed from Will County.
What Grows in Wilmington
Every plant below cleared Wilmington's own zone 5b and its 201-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Wilmington?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 28 — 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.
Documented around Wilmington
Spotted lanternfly documented 25 miles from Wilmington, first recorded 2023. What to watch for.
What's on the federal record near Wilmington
Closest first, within ~10 miles of Wilmington. Listing isn't leaking, and distance isn't exposure.
- CELOTEX CORPORATED DUMPSuperfund · 0.8 mi
- Ryder Student TransportationUnderground Storage Tanks · 0.8 mi
- EVANS LAWN & GARDEN INCBrownfields · 0.9 mi
- SUPERIOR AUTO EMPORIUMBrownfields · 0.9 mi
- Des Plaines Game FarmUnderground Storage Tanks · 0.9 mi
- Marge Van Duyne Estate (Deceased)Underground Storage Tanks · 1.0 mi
- Clennon Electric IncUnderground Storage Tanks · 1.0 mi
- Mac's #185Underground Storage Tanks · 1.0 mi
- 33N 9E-25.6b2Nitrate · 1.0 mi
- Personal Products CoUnderground Storage Tanks · 1.0 mi
- City Of WilmingtonUnderground Storage Tanks · 1.0 mi
- Island City GarageUnderground Storage Tanks · 1.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Wilmington'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 Wilmington.
Sources Checked
within ~10 miles of Wilmington
Severity Distribution
within ~10 miles of Wilmington
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Wilmington, two things run higher than the national average within ~10 miles of Wilmington — Superfund (8 sites) and Toxics Release Inventory (29 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Wilmington
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 Wilmington average
Your land is one point inside Wilmington
Everything above resolves to Wilmington as a whole — one PHZM band and one 28°F frost record, read across 9K 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 Wilmington Average
Wilmington Average
- ●USDA Zones 5b, averaged across Wilmington
- ●One soil character for all of Wilmington
- ●Frost dates read at Wilmington's scale: Apr 10 to Oct 28
YOUR Parcel
- ✓Your exact zone, not Wilmington's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Wilmington
Pull a site-specific report for your exact address in Wilmington, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Wilmington averages can't show:
We read public map data around Wilmington — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Wilmington average
How we know this about Wilmington
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 Wilmington’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 Wilmington
When does frost risk typically end in Wilmington?
The last hard freeze (28°F) in Wilmington typically lands around Apr 10, 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 1.
When is the first frost in Wilmington?
The first hard freeze (28°F) in Wilmington typically arrives around Oct 28, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 14, so the watching starts about Sep 28 — about 201 days after the spring freeze cleared.
How long is the growing season in Wilmington?
Measured between 28°F hard freezes, Wilmington sees about 201 frost-free days — roughly Apr 10 through Oct 28, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 1 to Oct 14, about 166 days.
Is the soil safe to grow vegetables in Wilmington?
The federal record around Wilmington runs heavier than most — 276 documented sites, mostly Brownfields entries (111), the nearest Superfund record about 0.8 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do I protect my plants from frost in Wilmington?
From about Sep 28 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 28 (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 28. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Wilmington's scale — its 5b band and its 201-day season. Your yard writes its own version of Wilmington'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 Wilmington’s own scale
7 of the readings below were taken at Wilmington's own scale — its own ~201-day season between 28°F freezes, the 8,986 acres it covers and 276 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Wilmington's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Wilmington's own 28°F hard-freeze dates, about Apr 10 and Oct 28 and the ~201-day span between themNOAA 1991–2020 Climate Normals
- 276 documented contamination sites on the federal record near Wilmington, the closest Superfund record about 0.8 miles out from the town centreFederal environmental registers
- Wilmington's boundary and the 8,986 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~201-day seasonGrowable Ground crop-matching engine
- The ecoregion at Wilmington's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Wilmingtonlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Wilmington's 8,986 acres read through its county's SSURGO summaryfrom Will County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Will 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 Will County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Wilmington's 8,986 acreswhy one lot differs from the next →
- Which side of Wilmington you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 8,986 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Superfund record about 0.8 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 Wilmington-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisWilmington sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides