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

Planting zone for 62946 — Harrisburg, IL

ZIP code 62946 (Harrisburg, Saline County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 7 and the first fall frost October 26.

Where ZIP 62946 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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 7
First frostOct 26
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 Harrisburg, 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 Harrisburg, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 7median — 50% chance of a later frost
Safe for tender plantsApril 25only 10% chance of frost after
First fall frostOctober 26median — 10% chance by Oct 10
Growing season202 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 26 and returns around November 6.

From the NOAA station Harrisburg, IL — 2 miles away, elevation 364 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 62946

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 24 – Mar 10
SpinachSow outdoors · Feb 24 – Mar 17
Broccoli, cabbageStart indoors · Jan 27 – Feb 10
Broccoli, cabbageTransplant · Mar 17 – Mar 31
Onion setsPlant outdoors · Mar 10 – Mar 24
PotatoesPlant outdoors · Mar 17 – Mar 31
LettuceSow outdoors · Mar 10 – Mar 24
Carrots, beetsSow outdoors · Mar 17 – Mar 31
TomatoesStart indoors · Feb 10 – Feb 24
TomatoesTransplant · Apr 14 – Apr 28
Peppers, eggplantStart indoors · Jan 27 – Feb 10
Peppers, eggplantTransplant · Apr 21 – May 5
BeansSow outdoors · Apr 14 – Apr 28
Sweet cornSow outdoors · Apr 14 – Apr 28
Cucumbers, squashSow outdoors · Apr 14 – Apr 28
Fall lettuce, spinachSow outdoors · Aug 31 – Sep 14
GarlicPlant cloves · Oct 12 – Nov 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 7) and first fall frost (Oct 26) 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 62946 came on Mar 2 — 8 days earlier than the 1991–2020 average (Mar 10).

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 Harrisburg, IL.

Soil in Harrisburg, IL

The soil mapped at the center of ZIP 62946 is Patton — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH6.7neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter4.25%moderate
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Patton silty clay loam, 0 to 2 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 62946; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harrisburg, IL

Summer high89 °Faverage high, July
Winter low24 °Faverage low, January
Hot days43days a year at 90 °F or more
Freezing nights95nights a year at 32 °F or less
Growing degree days4,395base 50 °F — the season’s usable heat
Longest day14 h 46 mindaylight on June 21
Shortest day9 h 33 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation47.6 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 43 °F, low 24 °F 43°24° JanFebruary: average high 48 °F, low 28 °F 48°28° FebMarch: average high 58 °F, low 36 °F 58°36° MarApril: average high 69 °F, low 46 °F 69°46° AprMay: average high 78 °F, low 57 °F 78°57° MayJune: average high 86 °F, low 65 °F 86°65° JunJuly: average high 89 °F, low 68 °F 89°68° JulAugust: average high 88 °F, low 66 °F 88°66° AugSeptember: average high 82 °F, low 57 °F 82°57° SepOctober: average high 71 °F, low 45 °F 71°45° OctNovember: average high 57 °F, low 36 °F 57°36° NovDecember: average high 47 °F, low 29 °F 47°29° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.79 in precipitation 3.8 JanFebruary: 3.13 in precipitation 3.1 FebMarch: 4.90 in precipitation 4.9 MarApril: 5.26 in precipitation 5.3 AprMay: 4.31 in precipitation 4.3 MayJune: 4.92 in precipitation 4.9 JunJuly: 3.49 in precipitation 3.5 JulAugust: 3.58 in precipitation 3.6 AugSeptember: 3.10 in precipitation 3.1 SepOctober: 3.76 in precipitation 3.8 OctNovember: 3.97 in precipitation 4.0 NovDecember: 3.38 in precipitation 3.4 Dec

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

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

629657a
Muddy, IL · 5 mi
629177a
Carrier Mills, IL · 7 mi
629347a
Equality, IL · 9 mi
629877a
Stonefort, IL · 10 mi
629777a
Raleigh, IL · 11 mi
629307a
Eldorado, IL · 11 mi
629357a
Galatia, IL · 12 mi
629477a
Herod, IL · 12 mi

Illinois planting zones →

Questions about 62946

What planting zone is ZIP code 62946?

ZIP code 62946 (Harrisburg, 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 Harrisburg, IL?

The median last spring frost (32 °F) near 62946 is April 7; after April 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Harrisburg station.

When is the first frost in Harrisburg, IL?

The median first fall frost near 62946 is October 26, giving a median frost-free growing season of 202 days.

When should I plant tomatoes in 62946?

Start tomato seeds indoors around Feb 10 – Feb 24 and set transplants outside around Apr 14 – Apr 28, one to three weeks after the median last frost.

How much rain and snow does 62946 get?

About 47.6 inches of precipitation a year (NOAA 1991–2020 normals, Harrisburg station).

How hot do summers get in Harrisburg, IL?

The average high peaks at 89 °F in July, with about 43 days a year at 90 °F or more.

What kind of soil does 62946 have?

The USDA soil survey maps Patton at the center of ZIP 62946: silty clay loam, poorly drained, pH about 6.7 (neutral).

Did spring come early in Harrisburg, IL in 2026?

Spring leaf-out near 62946 came on Mar 2 in 2026, 8 days earlier than the 1991–2020 average (Mar 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harrisburg, IL?

Intermediate onions: the longest day near 62946 is 14 h 46 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 62946 change?

Yes. The 2012 USDA map put 62946 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.