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

Planting zone for 61435 — Gerlaw, IL

ZIP code 61435 (Gerlaw, Warren County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 22 and the first fall frost October 15.

Where ZIP 61435 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 22

First frostOct 15

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 Gerlaw, 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 Gerlaw, IL

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 22median — 50% chance of a later frost

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

First fall frostOctober 15median — 10% chance by Sep 29

Growing season174 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 11 and returns around October 25.

From the NOAA station Monmouth, IL — 5 miles away, elevation 722 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 61435

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 11 – Mar 25

SpinachSow outdoors · Mar 11 – Apr 1

Broccoli, cabbageStart indoors · Feb 11 – Feb 25

Broccoli, cabbageTransplant · Apr 1 – Apr 15

Onion setsPlant outdoors · Mar 25 – Apr 8

PotatoesPlant outdoors · Apr 1 – Apr 15

LettuceSow outdoors · Mar 25 – Apr 8

Carrots, beetsSow outdoors · Apr 1 – Apr 15

TomatoesStart indoors · Feb 25 – Mar 11

TomatoesTransplant · Apr 29 – May 13

Peppers, eggplantStart indoors · Feb 11 – Feb 25

Peppers, eggplantTransplant · May 6 – May 20

BeansSow outdoors · Apr 29 – May 13

Sweet cornSow outdoors · Apr 29 – May 13

Cucumbers, squashSow outdoors · Apr 29 – May 13

Fall lettuce, spinachSow outdoors · Aug 20 – Sep 3

GarlicPlant cloves · Oct 1 – Nov 5

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 22) and first fall frost (Oct 15) 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 61435 came on Mar 15 — 18 days earlier than the 1991–2020 average (Apr 2).

average
Apr 22026
Mar 15

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 Gerlaw, IL.

Soil in Gerlaw, IL

The soil mapped at the center of ZIP 61435 is Hickory — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.8neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter4%moderate

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Hickory silt loam, cool mesic, 35 to 60 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 61435; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Gerlaw, IL

Summer high84 °Faverage high, July

Winter low15 °Faverage low, January

Hot days20days a year at 90 °F or more

Freezing nights127nights a year at 32 °F or less

Growing degree days3,283base 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)

Precipitation38.2 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Monmouth, IL (5 mi away); precipitation: Alexis 1 Sw, IL (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

North Henderson, IL · 9 mi

614025b

Galesburg, IL · 9 mi

614015b

Galesburg, IL · 10 mi

614535b

Little York, IL · 10 mi

614395b

Henderson, IL · 12 mi

Illinois planting zones →

Questions about 61435

What planting zone is ZIP code 61435?

ZIP code 61435 (Gerlaw, 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 Gerlaw, IL?

The median last spring frost (32 °F) near 61435 is April 22; after May 10 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Monmouth station.

When is the first frost in Gerlaw, IL?

The median first fall frost near 61435 is October 15, giving a median frost-free growing season of 174 days.

When should I plant tomatoes in 61435?

Start tomato seeds indoors around Feb 25 – Mar 11 and set transplants outside around Apr 29 – May 13, one to three weeks after the median last frost.

How much rain and snow does 61435 get?

About 38.2 inches of precipitation a year (NOAA 1991–2020 normals, Alexis 1 Sw station).

How hot do summers get in Gerlaw, IL?

The average high peaks at 84 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 61435 have?

The USDA soil survey maps Hickory at the center of ZIP 61435: silt loam, well drained, pH about 6.8 (neutral).

Did spring come early in Gerlaw, IL in 2026?

Spring leaf-out near 61435 came on Mar 15 in 2026, 18 days earlier than the 1991–2020 average (Apr 2), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Gerlaw, IL?

Long-day onions: the longest day near 61435 is 15 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).