Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 60474 — South Wilmington, IL

ZIP code 60474 (South Wilmington, Grundy County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 27 and the first fall frost October 15.

Where ZIP 60474 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostApr 27
First frostOct 15
2012 zone5b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for South Wilmington, IL…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in South Wilmington, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 27median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 15median — 10% chance by Sep 30
Growing season170 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 17 and returns around October 25.

From the NOAA station Dwight, IL — 9 miles away, elevation 627 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 60474

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 16 – Mar 30
SpinachSow outdoors · Mar 16 – Apr 6
Broccoli, cabbageStart indoors · Feb 16 – Mar 2
Broccoli, cabbageTransplant · Apr 6 – Apr 20
Onion setsPlant outdoors · Mar 30 – Apr 13
PotatoesPlant outdoors · Apr 6 – Apr 20
LettuceSow outdoors · Mar 30 – Apr 13
Carrots, beetsSow outdoors · Apr 6 – Apr 20
TomatoesStart indoors · Mar 2 – Mar 16
TomatoesTransplant · May 4 – May 18
Peppers, eggplantStart indoors · Feb 16 – Mar 2
Peppers, eggplantTransplant · May 11 – May 25
BeansSow outdoors · May 4 – May 18
Sweet cornSow outdoors · May 4 – May 18
Cucumbers, squashSow outdoors · May 4 – May 18
Fall lettuce, spinachSow outdoors · Aug 20 – Sep 3
GarlicPlant cloves · Oct 1 – Nov 5
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 15) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 60474 came on Mar 18 — 17 days earlier than the 1991–2020 average (Apr 4).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 5b in Illinois

584 plants native to the lower 48 states, recorded in Illinois, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 77

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 102

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 210

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 173

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °F

Vines 7

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in South Wilmington, IL.

Soil in South Wilmington, IL

The soil mapped at the center of ZIP 60474 is Andres — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH7.0neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter4.2%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Andres silt loam, 0 to 2 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 60474; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South Wilmington, IL

Summer high84 °Faverage high, July
Winter low14 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights140nights a year at 32 °F or less
Growing degree days3,037base 50 °F — the season’s usable heat
Longest day15 h 09 mindaylight on June 21
Shortest day9 h 12 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation38.5 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 31 °F, low 14 °F 31°14° JanFebruary: average high 35 °F, low 17 °F 35°17° FebMarch: average high 48 °F, low 27 °F 48°27° MarApril: average high 61 °F, low 37 °F 61°37° AprMay: average high 72 °F, low 49 °F 72°49° MayJune: average high 81 °F, low 59 °F 81°59° JunJuly: average high 84 °F, low 62 °F 84°62° JulAugust: average high 82 °F, low 59 °F 82°59° AugSeptember: average high 77 °F, low 51 °F 77°51° SepOctober: average high 64 °F, low 40 °F 64°40° OctNovember: average high 49 °F, low 29 °F 49°29° NovDecember: average high 36 °F, low 20 °F 36°20° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.11 in precipitation 2.1 JanFebruary: 1.81 in precipitation 1.8 FebMarch: 2.45 in precipitation 2.5 MarApril: 3.70 in precipitation 3.7 AprMay: 4.64 in precipitation 4.6 MayJune: 4.62 in precipitation 4.6 JunJuly: 3.97 in precipitation 4.0 JulAugust: 4.14 in precipitation 4.1 AugSeptember: 3.32 in precipitation 3.3 SepOctober: 3.13 in precipitation 3.1 OctNovember: 2.58 in precipitation 2.6 NovDecember: 2.04 in precipitation 2.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Dwight, IL (9 mi away); precipitation: Coal City 0.4 N, IL (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

604245b
Gardner, IL · 3 mi
604075b
Braceville, IL · 3 mi
609355b
Essex, IL · 5 mi
609615b
Reddick, IL · 6 mi
604085b
Braidwood, IL · 6 mi
604165b
Coal City, IL · 7 mi
604445b
Mazon, IL · 8 mi
609695b
Union Hill, IL · 8 mi

Illinois planting zones →

Questions about 60474

What planting zone is ZIP code 60474?

ZIP code 60474 (South Wilmington, IL) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in South Wilmington, IL?

The median last spring frost (32 °F) near 60474 is April 27; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dwight station.

When is the first frost in South Wilmington, IL?

The median first fall frost near 60474 is October 15, giving a median frost-free growing season of 170 days.

When should I plant tomatoes in 60474?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 60474 get?

About 38.5 inches of precipitation a year (NOAA 1991–2020 normals, Coal City 0.4 N station).

How hot do summers get in South Wilmington, IL?

The average high peaks at 84 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 60474 have?

The USDA soil survey maps Andres at the center of ZIP 60474: silt loam, somewhat poorly drained, pH about 7.0 (neutral).

Did spring come early in South Wilmington, IL in 2026?

Spring leaf-out near 60474 came on Mar 18 in 2026, 17 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in South Wilmington, IL?

Long-day onions: the longest day near 60474 is 15 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).