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

Planting zone for Northbrook, IL

Northbrook, IL is in USDA zone 6a across its 2 ZIP codes. The median last spring frost is April 19 and the first fall frost October 26.

Northbrook on the zone map

Outlined: its 1 ZIP code areas · 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
ZIP codes2
Last frostApr 19
First frostOct 26
Growing season190 days

6a 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 Northbrook, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 19median — 50% chance of a later frost
Safe for tender plantsMay 3only 10% chance of frost after
First fall frostOctober 26median — 10% chance by Oct 13
Growing season190 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 5 and returns around November 7.

From the NOAA station Chicago Palwaukee Airport, IL, elevation 637 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 Northbrook

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 8 – Mar 22
SpinachSow outdoors · Mar 8 – Mar 29
Broccoli, cabbageStart indoors · Feb 8 – Feb 22
Broccoli, cabbageTransplant · Mar 29 – Apr 12
Onion setsPlant outdoors · Mar 22 – Apr 5
PotatoesPlant outdoors · Mar 29 – Apr 12
LettuceSow outdoors · Mar 22 – Apr 5
Carrots, beetsSow outdoors · Mar 29 – Apr 12
TomatoesStart indoors · Feb 22 – Mar 8
TomatoesTransplant · Apr 26 – May 10
Peppers, eggplantStart indoors · Feb 8 – Feb 22
Peppers, eggplantTransplant · May 3 – May 17
BeansSow outdoors · Apr 26 – May 10
Sweet cornSow outdoors · Apr 26 – May 10
Cucumbers, squashSow outdoors · Apr 26 – May 10
Fall lettuce, spinachSow outdoors · Aug 31 – Sep 14
GarlicPlant cloves · Oct 12 – Nov 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 19) and first fall frost (Oct 26) 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 60065 came on Mar 25 — 13 days earlier than the 1991–2020 average (Apr 7).

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 Northbrook, IL.

Soil in Northbrook, IL

The soil mapped at the center of ZIP 60065 is Orthents — silty clay, moderately well drained.

TextureSilty clayholds water and nutrients; slow to drain and warm up
pH6.7neutral; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter1.25%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Orthents, clayey, undulating.

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 60065; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Northbrook, IL

Summer high84 °Faverage high, July
Winter low16 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights128nights a year at 32 °F or less
Growing degree days2,963base 50 °F — the season’s usable heat
Longest day15 h 15 mindaylight on June 21
Shortest day9 h 06 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation39.5 inper year, rain and melted snow
Snowfall34 inper year; 53 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 32 °F, low 16 °F 32°16° JanFebruary: average high 36 °F, low 19 °F 36°19° FebMarch: average high 46 °F, low 28 °F 46°28° MarApril: average high 57 °F, low 38 °F 57°38° AprMay: average high 68 °F, low 48 °F 68°48° MayJune: average high 78 °F, low 57 °F 78°57° JunJuly: average high 84 °F, low 63 °F 84°63° JulAugust: average high 82 °F, low 62 °F 82°62° AugSeptember: average high 75 °F, low 55 °F 75°55° SepOctober: average high 63 °F, low 43 °F 63°43° OctNovember: average high 49 °F, low 33 °F 49°33° NovDecember: average high 38 °F, low 22 °F 38°22° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 2.10 in precipitation, 11.3 in snowfall 2.1❄11 JanFebruary: 1.98 in precipitation, 7.7 in snowfall 2.0❄8 FebMarch: 2.26 in precipitation, 5.6 in snowfall 2.3❄6 MarApril: 4.00 in precipitation, 1.1 in snowfall 4.0❄1 AprMay: 4.84 in precipitation 4.8 MayJune: 4.31 in precipitation 4.3 JunJuly: 3.74 in precipitation 3.7 JulAugust: 4.16 in precipitation 4.2 AugSeptember: 3.56 in precipitation 3.6 SepOctober: 3.59 in precipitation, 0.1 in snowfall 3.6 OctNovember: 2.63 in precipitation, 1.9 in snowfall 2.6❄2 NovDecember: 2.34 in precipitation, 5.9 in snowfall 2.3❄6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Chicago Botanic Garden, IL (2 mi away); precipitation: Chicago Botanic Garden, IL (2 mi away). Daylight is calculated from latitude.

ZIP codes in Northbrook

600626a
−10 to −5 °F
600656a
−10 to −5 °F

Illinois planting zones →

Questions about Northbrook

What planting zone is Northbrook, IL?

Northbrook, IL is in USDA hardiness zone 6a on the 2023 map (6a: −10 to −5 °F).

When is the last frost in Northbrook, IL?

The median last spring frost is April 19 and the median first fall frost is October 26 (NOAA 1991–2020 normals, Chicago Palwaukee Airport station).

When can I plant a garden in Northbrook, IL?

Cool-season crops like peas and spinach go in around Mar 8 – Mar 29; tomatoes, peppers, beans and squash after about Apr 26, once frost risk has passed.

What kind of onions grow in Northbrook, IL?

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

How much rain and snow does Northbrook, IL get?

About 39.5 inches of precipitation a year and 34 inches of snowfall (NOAA 1991–2020 normals).