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

Planting zone for 62666 — Middletown, IL

ZIP code 62666 (Middletown, Logan County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 17 and the first fall frost October 18.

Where ZIP 62666 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostApr 17

First frostOct 18

2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Middletown, 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 Middletown, IL

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 17median — 50% chance of a later frost

Safe for tender plantsMay 4only 10% chance of frost after

First fall frostOctober 18median — 10% chance by Oct 4

Growing season182 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 6 and returns around October 29.

From the NOAA station Mason City 4se, IL — 8 miles away, elevation 600 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 62666

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 6 – Mar 20

SpinachSow outdoors · Mar 6 – Mar 27

Broccoli, cabbageStart indoors · Feb 6 – Feb 20

Broccoli, cabbageTransplant · Mar 27 – Apr 10

Onion setsPlant outdoors · Mar 20 – Apr 3

PotatoesPlant outdoors · Mar 27 – Apr 10

LettuceSow outdoors · Mar 20 – Apr 3

Carrots, beetsSow outdoors · Mar 27 – Apr 10

TomatoesStart indoors · Feb 20 – Mar 6

TomatoesTransplant · Apr 24 – May 8

Peppers, eggplantStart indoors · Feb 6 – Feb 20

Peppers, eggplantTransplant · May 1 – May 15

BeansSow outdoors · Apr 24 – May 8

Sweet cornSow outdoors · Apr 24 – May 8

Cucumbers, squashSow outdoors · Apr 24 – May 8

Fall lettuce, spinachSow outdoors · Aug 23 – Sep 6

GarlicPlant cloves · Oct 4 – Nov 8

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 17) and first fall frost (Oct 18) 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 62666 came on Mar 11 — 15 days earlier than the 1991–2020 average (Mar 26).

average
Mar 262026
Mar 11

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.

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 Middletown, IL.

Soil in Middletown, IL

The soil mapped at the center of ZIP 62666 is Tama — 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 matter3.5%moderate

Hydrologic groupBwater soaks in moderately

Farmland classprime farmlandUSDA classification

Map unit: Tama silt loam, very deep to sand, 2 to 5 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 62666; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Middletown, IL

Summer high85 °Faverage high, July

Winter low16 °Faverage low, January

Hot days27days a year at 90 °F or more

Freezing nights122nights a year at 32 °F or less

Growing degree days3,481base 50 °F — the season’s usable heat

Longest day15 h 01 mindaylight on June 21

Shortest day9 h 19 mindaylight on December 21

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

Precipitation39.2 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: Mason City 4se, IL (8 mi away); precipitation: Lincoln 4.6 W, IL (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

626716a

New Holland, IL · 6 mi

626346a

Elkhart, IL · 7 mi

626936a

Williamsville, IL · 9 mi

626136a

Athens, IL · 10 mi

626426a

Greenview, IL · 10 mi

626566a

Lincoln, IL · 10 mi

626436a

Hartsburg, IL · 12 mi

626846a

Sherman, IL · 12 mi

Illinois planting zones →

Questions about 62666

What planting zone is ZIP code 62666?

ZIP code 62666 (Middletown, IL) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Middletown, IL?

The median last spring frost (32 °F) near 62666 is April 17; after May 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mason City 4se station.

When is the first frost in Middletown, IL?

The median first fall frost near 62666 is October 18, giving a median frost-free growing season of 182 days.

When should I plant tomatoes in 62666?

Start tomato seeds indoors around Feb 20 – Mar 6 and set transplants outside around Apr 24 – May 8, one to three weeks after the median last frost.

How much rain and snow does 62666 get?

About 39.2 inches of precipitation a year (NOAA 1991–2020 normals, Lincoln 4.6 W station).

How hot do summers get in Middletown, IL?

The average high peaks at 85 °F in July, with about 27 days a year at 90 °F or more.

What kind of soil does 62666 have?

The USDA soil survey maps Tama at the center of ZIP 62666: silt loam, well drained, pH about 6.6 (neutral).

Did spring come early in Middletown, IL in 2026?

Spring leaf-out near 62666 came on Mar 11 in 2026, 15 days earlier than the 1991–2020 average (Mar 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Middletown, IL?

Long-day onions: the longest day near 62666 is 15 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 62666 change?

Yes. The 2012 USDA map put 62666 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.