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

Planting zone for 62237 — Coulterville, IL

ZIP code 62237 (Coulterville, Randolph County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 12 and the first fall frost October 22.

Where ZIP 62237 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostApr 12
First frostOct 22
2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Coulterville, 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 Coulterville, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 12median — 50% chance of a later frost
Safe for tender plantsApril 29only 10% chance of frost after
First fall frostOctober 22median — 10% chance by Oct 7
Growing season191 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 1 and returns around November 1.

From the NOAA station Sparta 1 W, IL — 10 miles away, elevation 535 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 62237

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 1 – Mar 15
SpinachSow outdoors · Mar 1 – Mar 22
Broccoli, cabbageStart indoors · Feb 1 – Feb 15
Broccoli, cabbageTransplant · Mar 22 – Apr 5
Onion setsPlant outdoors · Mar 15 – Mar 29
PotatoesPlant outdoors · Mar 22 – Apr 5
LettuceSow outdoors · Mar 15 – Mar 29
Carrots, beetsSow outdoors · Mar 22 – Apr 5
TomatoesStart indoors · Feb 15 – Mar 1
TomatoesTransplant · Apr 19 – May 3
Peppers, eggplantStart indoors · Feb 1 – Feb 15
Peppers, eggplantTransplant · Apr 26 – May 10
BeansSow outdoors · Apr 19 – May 3
Sweet cornSow outdoors · Apr 19 – May 3
Cucumbers, squashSow outdoors · Apr 19 – May 3
Fall lettuce, spinachSow outdoors · Aug 27 – Sep 10
GarlicPlant cloves · Oct 8 – Nov 12
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 12) and first fall frost (Oct 22) 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 62237 came on Mar 2 — 12 days earlier than the 1991–2020 average (Mar 14).

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 6b in Illinois

620 plants native to the lower 48 states, recorded in Illinois, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 80

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 108

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 222

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 182

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °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 °F

Vines 11

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °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 Coulterville, IL.

Soil in Coulterville, IL

The soil mapped at the center of ZIP 62237 is Cisne — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
pH5.8moderately acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter1.75%low — add compost
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Cisne 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 62237; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Coulterville, IL

Summer high88 °Faverage high, July
Winter low22 °Faverage low, January
Hot days35days a year at 90 °F or more
Freezing nights109nights a year at 32 °F or less
Growing degree days3,944base 50 °F — the season’s usable heat
Longest day14 h 49 mindaylight on June 21
Shortest day9 h 30 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation45.6 inper year, rain and melted snow
Snowfall11 inper year

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 40 °F, low 22 °F 40°22° JanFebruary: average high 45 °F, low 25 °F 45°25° FebMarch: average high 56 °F, low 33 °F 56°33° MarApril: average high 67 °F, low 43 °F 67°43° AprMay: average high 76 °F, low 54 °F 76°54° MayJune: average high 84 °F, low 62 °F 84°62° JunJuly: average high 88 °F, low 66 °F 88°66° JulAugust: average high 87 °F, low 64 °F 87°64° AugSeptember: average high 81 °F, low 55 °F 81°55° SepOctober: average high 70 °F, low 44 °F 70°44° OctNovember: average high 56 °F, low 35 °F 56°35° NovDecember: average high 44 °F, low 26 °F 44°26° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.11 in precipitation, 3.5 in snowfall 3.1❄4 JanFebruary: 2.57 in precipitation, 3.4 in snowfall 2.6❄3 FebMarch: 3.95 in precipitation, 0.6 in snowfall 4.0❄1 MarApril: 5.16 in precipitation 5.2 AprMay: 5.17 in precipitation 5.2 MayJune: 4.31 in precipitation 4.3 JunJuly: 4.68 in precipitation 4.7 JulAugust: 3.54 in precipitation 3.5 AugSeptember: 3.03 in precipitation 3.0 SepOctober: 3.34 in precipitation 3.3 OctNovember: 4.08 in precipitation, 0.5 in snowfall 4.1❄1 NovDecember: 2.70 in precipitation, 2.6 in snowfall 2.7❄3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Sparta 1 W, IL (10 mi away); precipitation: Sparta 1 W, IL (10 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

622686b
Oakdale, IL · 6 mi
622927a
Tilden, IL · 6 mi
622867a
Sparta, IL · 10 mi
622387a
Cutler, IL · 10 mi
622577a
Marissa, IL · 11 mi
622747a
Pinckneyville, IL · 12 mi
622636b
Nashville, IL · 12 mi
622146b
Addieville, IL · 12 mi

Illinois planting zones →

Questions about 62237

What planting zone is ZIP code 62237?

ZIP code 62237 (Coulterville, IL) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Coulterville, IL?

The median last spring frost (32 °F) near 62237 is April 12; after April 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sparta 1 W station.

When is the first frost in Coulterville, IL?

The median first fall frost near 62237 is October 22, giving a median frost-free growing season of 191 days.

When should I plant tomatoes in 62237?

Start tomato seeds indoors around Feb 15 – Mar 1 and set transplants outside around Apr 19 – May 3, one to three weeks after the median last frost.

How much rain and snow does 62237 get?

About 45.6 inches of precipitation a year and 11 inches of snowfall (NOAA 1991–2020 normals, Sparta 1 W station).

How hot do summers get in Coulterville, IL?

The average high peaks at 88 °F in July, with about 35 days a year at 90 °F or more.

What kind of soil does 62237 have?

The USDA soil survey maps Cisne at the center of ZIP 62237: silt loam, poorly drained, pH about 5.8 (moderately acidic).

Did spring come early in Coulterville, IL in 2026?

Spring leaf-out near 62237 came on Mar 2 in 2026, 12 days earlier than the 1991–2020 average (Mar 14), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Coulterville, IL?

Intermediate onions: the longest day near 62237 is 14 h 49 min, so day-neutral types bulb best; long-day varieties may not bulb fully.