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

Planting zone for 61439 — Henderson, IL

ZIP code 61439 (Henderson, Knox County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 20 and the first fall frost October 19.

Where ZIP 61439 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 20
First frostOct 19
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Henderson, 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 Henderson, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 20median — 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 28.

From the NOAA station Galesburg, IL — 6 miles away, elevation 761 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 61439

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 9 – Mar 23
SpinachSow outdoors · Mar 9 – Mar 30
Broccoli, cabbageStart indoors · Feb 9 – Feb 23
Broccoli, cabbageTransplant · Mar 30 – Apr 13
Onion setsPlant outdoors · Mar 23 – Apr 6
PotatoesPlant outdoors · Mar 30 – Apr 13
LettuceSow outdoors · Mar 23 – Apr 6
Carrots, beetsSow outdoors · Mar 30 – Apr 13
TomatoesStart indoors · Feb 23 – Mar 9
TomatoesTransplant · Apr 27 – May 11
Peppers, eggplantStart indoors · Feb 9 – Feb 23
Peppers, eggplantTransplant · May 4 – May 18
BeansSow outdoors · Apr 27 – May 11
Sweet cornSow outdoors · Apr 27 – May 11
Cucumbers, squashSow outdoors · Apr 27 – May 11
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 20) 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 61439 came on Mar 15 — 20 days earlier than the 1991–2020 average (Apr 4).

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.

Trees 77

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 102

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 210

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 173

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 7

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °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 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °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 Henderson, IL.

Soil in Henderson, IL

The soil mapped at the center of ZIP 61439 is Osco — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.6neutral; 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: Osco 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 61439; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Henderson, IL

Summer high84 °Faverage high, July
Winter low14 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights129nights a year at 32 °F or less
Growing degree days3,330base 50 °F — the season’s usable heat
Longest day15 h 08 mindaylight on June 21
Shortest day9 h 13 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation39 inper year, rain and melted snow
Snowfall26 inper year; 42 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 30 °F, low 14 °F 30°14° JanFebruary: average high 35 °F, low 17 °F 35°17° FebMarch: average high 48 °F, low 28 °F 48°28° MarApril: average high 61 °F, low 40 °F 61°40° AprMay: average high 72 °F, low 52 °F 72°52° MayJune: average high 81 °F, low 62 °F 81°62° JunJuly: average high 84 °F, low 65 °F 84°65° JulAugust: average high 82 °F, low 63 °F 82°63° AugSeptember: average high 76 °F, low 55 °F 76°55° SepOctober: average high 63 °F, low 43 °F 63°43° OctNovember: average high 48 °F, low 30 °F 48°30° NovDecember: average high 35 °F, low 20 °F 35°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 1.69 in precipitation, 9 in snowfall 1.7❄9 JanFebruary: 1.87 in precipitation, 6.6 in snowfall 1.9❄7 FebMarch: 2.39 in precipitation, 2.3 in snowfall 2.4❄2 MarApril: 3.83 in precipitation, 0.4 in snowfall 3.8 AprMay: 5.27 in precipitation 5.3 MayJune: 4.58 in precipitation 4.6 JunJuly: 4.04 in precipitation 4.0 JulAugust: 3.89 in precipitation 3.9 AugSeptember: 3.85 in precipitation 3.9 SepOctober: 2.82 in precipitation 2.8 OctNovember: 2.60 in precipitation, 1.7 in snowfall 2.6❄2 NovDecember: 2.14 in precipitation, 5.9 in snowfall 2.1❄6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Galesburg, IL (6 mi away); precipitation: Galesburg, IL (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

614885b
Wataga, IL · 2 mi
614725b
Rio, IL · 5 mi
614015b
Galesburg, IL · 6 mi
614305b
East Galesburg, IL · 6 mi
614675b
Oneida, IL · 6 mi
614025b
Galesburg, IL · 7 mi
614485b
Knoxville, IL · 9 mi
614665b
North Henderson, IL · 9 mi

Illinois planting zones →

Questions about 61439

What planting zone is ZIP code 61439?

ZIP code 61439 (Henderson, 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 Henderson, IL?

The median last spring frost (32 °F) near 61439 is April 20; after May 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Galesburg station.

When is the first frost in Henderson, IL?

The median first fall frost near 61439 is October 19, giving a median frost-free growing season of 180 days.

When should I plant tomatoes in 61439?

Start tomato seeds indoors around Feb 23 – Mar 9 and set transplants outside around Apr 27 – May 11, one to three weeks after the median last frost.

How much rain and snow does 61439 get?

About 39 inches of precipitation a year and 26 inches of snowfall (NOAA 1991–2020 normals, Galesburg station).

How hot do summers get in Henderson, IL?

The average high peaks at 84 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 61439 have?

The USDA soil survey maps Osco at the center of ZIP 61439: silt loam, well drained, pH about 6.6 (neutral).

Did spring come early in Henderson, IL in 2026?

Spring leaf-out near 61439 came on Mar 15 in 2026, 20 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Henderson, IL?

Long-day onions: the longest day near 61439 is 15 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).