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

Planting zone for 62864 — Mount Vernon, IL

ZIP code 62864 (Mount Vernon, Jefferson County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 11 and the first fall frost October 22.

Where ZIP 62864 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.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostApr 11

First frostOct 22

2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Vernon, 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 Mount Vernon, IL

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 11median — 50% chance of a later frost

Safe for tender plantsApril 26only 10% chance of frost after

First fall frostOctober 22median — 10% chance by Oct 9

Growing season193 daysfrost-free, median

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

From the NOAA station Mt Vernon 3 Ne, IL — 3 miles away, elevation 489 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 62864

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 28 – Mar 14

SpinachSow outdoors · Feb 28 – Mar 21

Broccoli, cabbageStart indoors · Jan 31 – Feb 14

Broccoli, cabbageTransplant · Mar 21 – Apr 4

Onion setsPlant outdoors · Mar 14 – Mar 28

PotatoesPlant outdoors · Mar 21 – Apr 4

LettuceSow outdoors · Mar 14 – Mar 28

Carrots, beetsSow outdoors · Mar 21 – Apr 4

TomatoesStart indoors · Feb 14 – Feb 28

TomatoesTransplant · Apr 18 – May 2

Peppers, eggplantStart indoors · Jan 31 – Feb 14

Peppers, eggplantTransplant · Apr 25 – May 9

BeansSow outdoors · Apr 18 – May 2

Sweet cornSow outdoors · Apr 18 – May 2

Cucumbers, squashSow outdoors · Apr 18 – May 2

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 11) 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 62864 came on Mar 6 — 11 days earlier than the 1991–2020 average (Mar 17).

average
Mar 172026
Mar 6

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).

Soil in Mount Vernon, IL

The soil mapped at the center of ZIP 62864 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 62864; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Vernon, IL

Summer high86 °Faverage high, July

Winter low22 °Faverage low, January

Hot days21days a year at 90 °F or more

Freezing nights108nights a year at 32 °F or less

Growing degree days3,832base 50 °F — the season’s usable heat

Longest day14 h 50 mindaylight on June 21

Shortest day9 h 29 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation45 inper year, rain and melted snow

Snowfall10 inper year; 11 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mt Vernon 3 Ne, IL (3 mi away); precipitation: Mt Vernon 3 Ne, IL (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

Waltonville, IL · 11 mi

628936b

Walnut Hill, IL · 12 mi

Illinois planting zones →

Questions about 62864

What planting zone is ZIP code 62864?

ZIP code 62864 (Mount Vernon, IL) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Mount Vernon, IL?

The median last spring frost (32 °F) near 62864 is April 11; after April 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mt Vernon 3 Ne station.

When is the first frost in Mount Vernon, IL?

The median first fall frost near 62864 is October 22, giving a median frost-free growing season of 193 days.

When should I plant tomatoes in 62864?

Start tomato seeds indoors around Feb 14 – Feb 28 and set transplants outside around Apr 18 – May 2, one to three weeks after the median last frost.

How much rain and snow does 62864 get?

About 45 inches of precipitation a year and 10 inches of snowfall (NOAA 1991–2020 normals, Mt Vernon 3 Ne station).

How hot do summers get in Mount Vernon, IL?

The average high peaks at 86 °F in July, with about 21 days a year at 90 °F or more.

What kind of soil does 62864 have?

The USDA soil survey maps Ava at the center of ZIP 62864: silt loam, moderately well drained, pH about 6.3 (slightly acidic).

Did spring come early in Mount Vernon, IL in 2026?

Spring leaf-out near 62864 came on Mar 6 in 2026, 11 days earlier than the 1991–2020 average (Mar 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Vernon, IL?

Intermediate onions: the longest day near 62864 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 62864 change?

Yes. The 2012 USDA map put 62864 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.