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

Planting zone for 60559 — Westmont, IL

ZIP code 60559 (Westmont, 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 60559 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 Westmont, 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 Westmont, 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 60559

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 60559 came on Mar 21 — 15 days earlier than the 1991–2020 average (Apr 5).

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.

Trees 78

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 220

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 178

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 9

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 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °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 Westmont, IL.

Soil in Westmont, IL

The soil mapped at the center of ZIP 60559 is Markham — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH5.8moderately acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter3%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Markham-Ashkum-Beecher complex, 1 to 6 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 60559; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Westmont, 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)
Precipitation42.3 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 32 °F, low 15 °F 32°15° JanFebruary: average high 35 °F, low 18 °F 35°18° FebMarch: average high 47 °F, low 26 °F 47°26° MarApril: average high 59 °F, low 36 °F 59°36° AprMay: average high 71 °F, low 47 °F 71°47° MayJune: average high 81 °F, low 58 °F 81°58° JunJuly: average high 84 °F, low 62 °F 84°62° JulAugust: average high 83 °F, low 60 °F 83°60° AugSeptember: average high 76 °F, low 52 °F 76°52° SepOctober: average high 63 °F, low 40 °F 63°40° OctNovember: average high 48 °F, low 30 °F 48°30° NovDecember: average high 37 °F, low 21 °F 37°21° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.23 in precipitation 2.2 JanFebruary: 2.18 in precipitation 2.2 FebMarch: 2.59 in precipitation 2.6 MarApril: 3.88 in precipitation 3.9 AprMay: 4.87 in precipitation 4.9 MayJune: 4.91 in precipitation 4.9 JunJuly: 4.26 in precipitation 4.3 JulAugust: 4.62 in precipitation 4.6 AugSeptember: 3.28 in precipitation 3.3 SepOctober: 4.09 in precipitation 4.1 OctNovember: 2.91 in precipitation 2.9 NovDecember: 2.45 in precipitation 2.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Lisle-Morton Arboretum, IL (6 mi away); precipitation: Downers Grove 0.4 Nne, IL (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

605146a
Clarendon Hills, IL · <1 mi
605216a
Hinsdale, IL · 2 mi
605156a
Downers Grove, IL · 3 mi
605236a
Oak Brook, IL · 3 mi
605165b
Downers Grove, IL · 3 mi
605616a
Darien, IL · 3 mi
605586a
Western Springs, IL · 4 mi
605276a
Willowbrook, IL · 4 mi

Illinois planting zones →

Questions about 60559

What planting zone is ZIP code 60559?

ZIP code 60559 (Westmont, 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 Westmont, IL?

The median last spring frost (32 °F) near 60559 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 Westmont, IL?

The median first fall frost near 60559 is October 16, giving a median frost-free growing season of 169 days.

When should I plant tomatoes in 60559?

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 60559 get?

About 42.3 inches of precipitation a year (NOAA 1991–2020 normals, Downers Grove 0.4 Nne station).

How hot do summers get in Westmont, 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 60559 have?

The USDA soil survey maps Markham at the center of ZIP 60559: silt loam, moderately well drained, pH about 5.8 (moderately acidic).

Did spring come early in Westmont, IL in 2026?

Spring leaf-out near 60559 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 Westmont, IL?

Long-day onions: the longest day near 60559 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 60559 change?

Yes. The 2012 USDA map put 60559 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.