Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 60523 — Oak Brook, IL

ZIP code 60523 (Oak Brook, DuPage County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 28 and the first fall frost October 16.

Where ZIP 60523 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostApr 28

First frostOct 16

2012 zone5b

Was 5b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Oak Brook, 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 Oak Brook, IL

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 28median — 50% chance of a later frost

Safe for tender plantsMay 14only 10% chance of frost after

First fall frostOctober 16median — 10% chance by Oct 1

Growing season169 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 16 and returns around October 26.

From the NOAA station Lisle-Morton Arboretum, IL — 6 miles away, elevation 679 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 60523

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 17 – Mar 31

SpinachSow outdoors · Mar 17 – Apr 7

Broccoli, cabbageStart indoors · Feb 17 – Mar 3

Broccoli, cabbageTransplant · Apr 7 – Apr 21

Onion setsPlant outdoors · Mar 31 – Apr 14

PotatoesPlant outdoors · Apr 7 – Apr 21

LettuceSow outdoors · Mar 31 – Apr 14

Carrots, beetsSow outdoors · Apr 7 – Apr 21

TomatoesStart indoors · Mar 3 – Mar 17

TomatoesTransplant · May 5 – May 19

Peppers, eggplantStart indoors · Feb 17 – Mar 3

Peppers, eggplantTransplant · May 12 – May 26

BeansSow outdoors · May 5 – May 19

Sweet cornSow outdoors · May 5 – May 19

Cucumbers, squashSow outdoors · May 5 – May 19

Fall lettuce, spinachSow outdoors · Aug 21 – Sep 4

GarlicPlant cloves · Oct 2 – Nov 6

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 16) 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 60523 came on Mar 21 — 15 days earlier than the 1991–2020 average (Apr 5).

average
Apr 52026
Mar 21

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 6a in Illinois

610 plants native to the lower 48 states, recorded in Illinois, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

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 Oak Brook, IL.

Soil in Oak Brook, IL

The soil mapped at the center of ZIP 60523 is Ozaukee — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables

pH6.8neutral; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter1.7%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classprime farmlandUSDA classification

Map unit: Ozaukee silt loam, 4 to 6 percent slopes, eroded.

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 60523; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Oak Brook, IL

Summer high84 °Faverage high, July

Winter low15 °Faverage low, January

Hot days17days a year at 90 °F or more

Freezing nights144nights a year at 32 °F or less

Growing degree days2,957base 50 °F — the season’s usable heat

Longest day15 h 13 mindaylight on June 21

Shortest day9 h 08 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation39.7 inper year, rain and melted snow

Snowfall42 inper year; 55 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Lisle-Morton Arboretum, IL (6 mi away); precipitation: Oak Brook 2w, IL (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

605216a

Hinsdale, IL · 3 mi

605146a

Clarendon Hills, IL · 3 mi

601816a

Villa Park, IL · 3 mi

605596a

Westmont, IL · 3 mi

601546a

Westchester, IL · 3 mi

601626a

Hillside, IL · 3 mi

605266a

La Grange Park, IL · 4 mi

605586a

Western Springs, IL · 4 mi

Illinois planting zones →

Questions about 60523

What planting zone is ZIP code 60523?

ZIP code 60523 (Oak Brook, IL) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Oak Brook, IL?

The median last spring frost (32 °F) near 60523 is April 28; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Lisle-Morton Arboretum station.

When is the first frost in Oak Brook, IL?

The median first fall frost near 60523 is October 16, giving a median frost-free growing season of 169 days.

When should I plant tomatoes in 60523?

Start tomato seeds indoors around Mar 3 – Mar 17 and set transplants outside around May 5 – May 19, one to three weeks after the median last frost.

How much rain and snow does 60523 get?

About 39.7 inches of precipitation a year and 42 inches of snowfall (NOAA 1991–2020 normals, Oak Brook 2w station).

How hot do summers get in Oak Brook, IL?

The average high peaks at 84 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 60523 have?

The USDA soil survey maps Ozaukee at the center of ZIP 60523: silt loam, moderately well drained, pH about 6.8 (neutral).

Did spring come early in Oak Brook, IL in 2026?

Spring leaf-out near 60523 came on Mar 21 in 2026, 15 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Oak Brook, IL?

Long-day onions: the longest day near 60523 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 60523 change?

Yes. The 2012 USDA map put 60523 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.