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

Planting zone for 61091 — Woosung, IL

ZIP code 61091 (Woosung, Ogle County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 21 and the first fall frost October 19.

Where ZIP 61091 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 21

First frostOct 19

2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Woosung, 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 Woosung, IL

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 21median — 50% chance of a later frost

Safe for tender plantsMay 5only 10% chance of frost after

First fall frostOctober 19median — 10% chance by Oct 4

Growing season180 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 10 and returns around October 30.

From the NOAA station Dixon 1w, IL — 6 miles away, elevation 659 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 61091

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 10 – Mar 24

SpinachSow outdoors · Mar 10 – Mar 31

Broccoli, cabbageStart indoors · Feb 10 – Feb 24

Broccoli, cabbageTransplant · Mar 31 – Apr 14

Onion setsPlant outdoors · Mar 24 – Apr 7

PotatoesPlant outdoors · Mar 31 – Apr 14

LettuceSow outdoors · Mar 24 – Apr 7

Carrots, beetsSow outdoors · Mar 31 – Apr 14

TomatoesStart indoors · Feb 24 – Mar 10

TomatoesTransplant · Apr 28 – May 12

Peppers, eggplantStart indoors · Feb 10 – Feb 24

Peppers, eggplantTransplant · May 5 – May 19

BeansSow outdoors · Apr 28 – May 12

Sweet cornSow outdoors · Apr 28 – May 12

Cucumbers, squashSow outdoors · Apr 28 – May 12

Fall lettuce, spinachSow outdoors · Aug 24 – Sep 7

GarlicPlant cloves · Oct 5 – Nov 9

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 21) and first fall frost (Oct 19) 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 61091 came on Mar 25 — 13 days earlier than the 1991–2020 average (Apr 7).

average
Apr 72026
Mar 25

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.

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 Woosung, IL.

Soil in Woosung, IL

The soil mapped at the center of ZIP 61091 is Parkway — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.2slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2.5%moderate

Hydrologic groupBwater soaks in moderately

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Parkway silt loam, 5 to 10 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 61091; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Woosung, IL

Summer high83 °Faverage high, July

Winter low14 °Faverage low, January

Hot days11days a year at 90 °F or more

Freezing nights138nights a year at 32 °F or less

Growing degree days3,126base 50 °F — the season’s usable heat

Longest day15 h 14 mindaylight on June 21

Shortest day9 h 07 mindaylight on December 21

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

Precipitation40.5 inper year, rain and melted snow

Snowfall31 inper year; 49 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: Dixon 1w, IL (6 mi away); precipitation: Dixon 1w, IL (6 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.

Mount Morris, IL · 12 mi

610515a

Milledgeville, IL · 12 mi

610615b

Oregon, IL · 12 mi

610315b

Franklin Grove, IL · 13 mi

Illinois planting zones →

Questions about 61091

What planting zone is ZIP code 61091?

ZIP code 61091 (Woosung, 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 Woosung, IL?

The median last spring frost (32 °F) near 61091 is April 21; after May 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dixon 1w station.

When is the first frost in Woosung, IL?

The median first fall frost near 61091 is October 19, giving a median frost-free growing season of 180 days.

When should I plant tomatoes in 61091?

Start tomato seeds indoors around Feb 24 – Mar 10 and set transplants outside around Apr 28 – May 12, one to three weeks after the median last frost.

How much rain and snow does 61091 get?

About 40.5 inches of precipitation a year and 31 inches of snowfall (NOAA 1991–2020 normals, Dixon 1w station).

How hot do summers get in Woosung, IL?

The average high peaks at 83 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 61091 have?

The USDA soil survey maps Parkway at the center of ZIP 61091: silt loam, well drained, pH about 6.2 (slightly acidic).

Did spring come early in Woosung, IL in 2026?

Spring leaf-out near 61091 came on Mar 25 in 2026, 13 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Woosung, IL?

Long-day onions: the longest day near 61091 is 15 h 14 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 61091 change?

Yes. The 2012 USDA map put 61091 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.