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

Planting zone for 61327 — Hennepin, IL

ZIP code 61327 (Hennepin, Putnam County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 18 and the first fall frost October 22.

Where ZIP 61327 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 18
First frostOct 22
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 Hennepin, 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 Hennepin, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 18median — 50% chance of a later frost
Safe for tender plantsMay 3only 10% chance of frost after
First fall frostOctober 22median — 10% chance by Oct 7
Growing season188 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 6 and returns around November 1.

From the NOAA station Hennepin, IL — 2 miles away, elevation 515 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 61327

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 7 – Mar 21
SpinachSow outdoors · Mar 7 – Mar 28
Broccoli, cabbageStart indoors · Feb 7 – Feb 21
Broccoli, cabbageTransplant · Mar 28 – Apr 11
Onion setsPlant outdoors · Mar 21 – Apr 4
PotatoesPlant outdoors · Mar 28 – Apr 11
LettuceSow outdoors · Mar 21 – Apr 4
Carrots, beetsSow outdoors · Mar 28 – Apr 11
TomatoesStart indoors · Feb 21 – Mar 7
TomatoesTransplant · Apr 25 – May 9
Peppers, eggplantStart indoors · Feb 7 – Feb 21
Peppers, eggplantTransplant · May 2 – May 16
BeansSow outdoors · Apr 25 – May 9
Sweet cornSow outdoors · Apr 25 – May 9
Cucumbers, squashSow outdoors · Apr 25 – May 9
Fall lettuce, spinachSow outdoors · Aug 27 – Sep 10
GarlicPlant cloves · Oct 8 – Nov 12
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 18) and first fall frost (Oct 22) 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 61327 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 Hennepin, IL.

Soil in Hennepin, IL

The soil mapped at the center of ZIP 61327 is Ambraw — clay loam, poorly drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter2.55%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Ambraw clay loam, 0 to 2 percent slopes, occasionally flooded.

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 61327; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Hennepin, IL

Summer high85 °Faverage high, July
Winter low17 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights119nights a year at 32 °F or less
Growing degree days3,387base 50 °F — the season’s usable heat
Longest day15 h 09 mindaylight on June 21
Shortest day9 h 12 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation38.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 32 °F, low 17 °F 32°17° JanFebruary: average high 37 °F, low 20 °F 37°20° FebMarch: average high 50 °F, low 30 °F 50°30° MarApril: average high 64 °F, low 41 °F 64°41° AprMay: average high 74 °F, low 51 °F 74°51° MayJune: average high 82 °F, low 61 °F 82°61° JunJuly: average high 85 °F, low 65 °F 85°65° JulAugust: average high 83 °F, low 62 °F 83°62° AugSeptember: average high 77 °F, low 55 °F 77°55° SepOctober: average high 65 °F, low 43 °F 65°43° OctNovember: average high 50 °F, low 32 °F 50°32° NovDecember: average high 37 °F, low 22 °F 37°22° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 1.95 in precipitation 1.9 JanFebruary: 1.80 in precipitation 1.8 FebMarch: 2.46 in precipitation 2.5 MarApril: 3.85 in precipitation 3.9 AprMay: 4.76 in precipitation 4.8 MayJune: 4.55 in precipitation 4.5 JunJuly: 3.89 in precipitation 3.9 JulAugust: 3.77 in precipitation 3.8 AugSeptember: 3.45 in precipitation 3.5 SepOctober: 3.31 in precipitation 3.3 OctNovember: 2.60 in precipitation 2.6 NovDecember: 2.19 in precipitation 2.2 Dec

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

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

613405b
Mark, IL · 3 mi
613265b
Granville, IL · 4 mi
613155b
Bureau, IL · 5 mi
613225b
Depue, IL · 6 mi
613355b
Mc Nabb, IL · 6 mi
615605b
Putnam, IL · 7 mi
613165b
Cedar Point, IL · 9 mi
613625b
Spring Valley, IL · 9 mi

Illinois planting zones →

Questions about 61327

What planting zone is ZIP code 61327?

ZIP code 61327 (Hennepin, 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 Hennepin, IL?

The median last spring frost (32 °F) near 61327 is April 18; after May 3 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hennepin station.

When is the first frost in Hennepin, IL?

The median first fall frost near 61327 is October 22, giving a median frost-free growing season of 188 days.

When should I plant tomatoes in 61327?

Start tomato seeds indoors around Feb 21 – Mar 7 and set transplants outside around Apr 25 – May 9, one to three weeks after the median last frost.

How much rain and snow does 61327 get?

About 38.6 inches of precipitation a year (NOAA 1991–2020 normals, Hennepin station).

How hot do summers get in Hennepin, IL?

The average high peaks at 85 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 61327 have?

The USDA soil survey maps Ambraw at the center of ZIP 61327: clay loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Hennepin, IL in 2026?

Spring leaf-out near 61327 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 Hennepin, IL?

Long-day onions: the longest day near 61327 is 15 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).