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

Planting zone for 62840 — Frankfort Heights, IL

ZIP code 62840 (Frankfort Heights, Franklin County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 4 and the first fall frost October 28.

Where ZIP 62840 is

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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 4
First frostOct 28
2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Frankfort Heights, 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 Frankfort Heights, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 4median — 50% chance of a later frost
Safe for tender plantsApril 21only 10% chance of frost after
First fall frostOctober 28median — 10% chance by Oct 15
Growing season206 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 25 and returns around November 7.

From the NOAA station Benton 2 N, IL — 3 miles away, elevation 446 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 62840

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 21 – Mar 7
SpinachSow outdoors · Feb 21 – Mar 14
Broccoli, cabbageStart indoors · Jan 24 – Feb 7
Broccoli, cabbageTransplant · Mar 14 – Mar 28
Onion setsPlant outdoors · Mar 7 – Mar 21
PotatoesPlant outdoors · Mar 14 – Mar 28
LettuceSow outdoors · Mar 7 – Mar 21
Carrots, beetsSow outdoors · Mar 14 – Mar 28
TomatoesStart indoors · Feb 7 – Feb 21
TomatoesTransplant · Apr 11 – Apr 25
Peppers, eggplantStart indoors · Jan 24 – Feb 7
Peppers, eggplantTransplant · Apr 18 – May 2
BeansSow outdoors · Apr 11 – Apr 25
Sweet cornSow outdoors · Apr 11 – Apr 25
Cucumbers, squashSow outdoors · Apr 11 – Apr 25
Fall lettuce, spinachSow outdoors · Sep 2 – Sep 16
GarlicPlant cloves · Oct 14 – Nov 18
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 4) and first fall frost (Oct 28) 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 62840 came on Mar 2 — 10 days earlier than the 1991–2020 average (Mar 12).

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 7a in Illinois

633 plants native to the lower 48 states, recorded in Illinois, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

Trees 81

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 110

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 226

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 186

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °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 °F

Vines 13

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fcupseed30 ft · blooms late spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °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 Frankfort Heights, IL.

Soil in Frankfort Heights, IL

The soil mapped at the center of ZIP 62840 is Ava — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.3slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Ava silt loam, 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 62840; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Frankfort Heights, IL

Summer high88 °Faverage high, July
Winter low25 °Faverage low, January
Hot days43days a year at 90 °F or more
Freezing nights93nights a year at 32 °F or less
Growing degree days4,190base 50 °F — the season’s usable heat
Longest day14 h 48 mindaylight on June 21
Shortest day9 h 31 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation46 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 41 °F, low 25 °F 41°25° JanFebruary: average high 44 °F, low 28 °F 44°28° FebMarch: average high 55 °F, low 37 °F 55°37° MarApril: average high 67 °F, low 46 °F 67°46° AprMay: average high 76 °F, low 56 °F 76°56° MayJune: average high 85 °F, low 64 °F 85°64° JunJuly: average high 88 °F, low 68 °F 88°68° JulAugust: average high 87 °F, low 66 °F 87°66° AugSeptember: average high 81 °F, low 58 °F 81°58° SepOctober: average high 68 °F, low 47 °F 68°47° OctNovember: average high 55 °F, low 37 °F 55°37° NovDecember: average high 44 °F, low 28 °F 44°28° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.18 in precipitation 3.2 JanFebruary: 2.80 in precipitation 2.8 FebMarch: 4.21 in precipitation 4.2 MarApril: 5.43 in precipitation 5.4 AprMay: 5.07 in precipitation 5.1 MayJune: 4.48 in precipitation 4.5 JunJuly: 3.96 in precipitation 4.0 JulAugust: 3.35 in precipitation 3.4 AugSeptember: 3.22 in precipitation 3.2 SepOctober: 3.44 in precipitation 3.4 OctNovember: 3.97 in precipitation 4.0 NovDecember: 2.89 in precipitation 2.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Benton 2 N, IL (3 mi away); precipitation: Rend Lake Dam, IL (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

628127a
Benton, IL · 1 mi
628197a
Buckner, IL · 4 mi
628917a
Valier, IL · 6 mi
628747a
Orient, IL · 6 mi
628227a
Christopher, IL · 6 mi
628566b
Logan, IL · 6 mi
628257a
Coello, IL · 6 mi
628976b
Whittington, IL · 7 mi

Illinois planting zones →

Questions about 62840

What planting zone is ZIP code 62840?

ZIP code 62840 (Frankfort Heights, IL) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Frankfort Heights, IL?

The median last spring frost (32 °F) near 62840 is April 4; after April 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Benton 2 N station.

When is the first frost in Frankfort Heights, IL?

The median first fall frost near 62840 is October 28, giving a median frost-free growing season of 206 days.

When should I plant tomatoes in 62840?

Start tomato seeds indoors around Feb 7 – Feb 21 and set transplants outside around Apr 11 – Apr 25, one to three weeks after the median last frost.

How much rain and snow does 62840 get?

About 46 inches of precipitation a year (NOAA 1991–2020 normals, Rend Lake Dam station).

How hot do summers get in Frankfort Heights, IL?

The average high peaks at 88 °F in July, with about 43 days a year at 90 °F or more.

What kind of soil does 62840 have?

The USDA soil survey maps Ava at the center of ZIP 62840: silt loam, moderately well drained, pH about 6.3 (slightly acidic).

Did spring come early in Frankfort Heights, IL in 2026?

Spring leaf-out near 62840 came on Mar 2 in 2026, 10 days earlier than the 1991–2020 average (Mar 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Frankfort Heights, IL?

Intermediate onions: the longest day near 62840 is 14 h 48 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 62840 change?

Yes. The 2012 USDA map put 62840 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.