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

Planting zone for 61370 — Tonica, IL

ZIP code 61370 (Tonica, LaSalle County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 24 and the first fall frost October 18.

Where ZIP 61370 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 24

First frostOct 18

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 Tonica, 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 Tonica, IL

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 24median — 50% chance of a later frost

Safe for tender plantsMay 8only 10% chance of frost after

First fall frostOctober 18median — 10% chance by Oct 3

Growing season176 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 13 and returns around October 28.

From the NOAA station Peru, IL — 11 miles away, elevation 620 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 61370

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 13 – Mar 27

SpinachSow outdoors · Mar 13 – Apr 3

Broccoli, cabbageStart indoors · Feb 13 – Feb 27

Broccoli, cabbageTransplant · Apr 3 – Apr 17

Onion setsPlant outdoors · Mar 27 – Apr 10

PotatoesPlant outdoors · Apr 3 – Apr 17

LettuceSow outdoors · Mar 27 – Apr 10

Carrots, beetsSow outdoors · Apr 3 – Apr 17

TomatoesStart indoors · Feb 27 – Mar 13

TomatoesTransplant · May 1 – May 15

Peppers, eggplantStart indoors · Feb 13 – Feb 27

Peppers, eggplantTransplant · May 8 – May 22

BeansSow outdoors · May 1 – May 15

Sweet cornSow outdoors · May 1 – May 15

Cucumbers, squashSow outdoors · May 1 – May 15

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 24) 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 61370 came on Mar 19 — 15 days earlier than the 1991–2020 average (Apr 3).

average
Apr 32026
Mar 19

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 Tonica, IL.

Soil in Tonica, IL

The soil mapped at the center of ZIP 61370 is Streator — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH7.0neutral; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter5.5%high

Hydrologic groupC/Dslow when drained; wet otherwise

Farmland classPrime farmland if drainedUSDA classification

Map unit: Streator 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 61370; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Tonica, IL

Summer high84 °Faverage high, July

Winter low14 °Faverage low, January

Hot days19days a year at 90 °F or more

Freezing nights139nights a year at 32 °F or less

Growing degree days3,121base 50 °F — the season’s usable heat

Longest day15 h 09 mindaylight on June 21

Shortest day9 h 12 mindaylight on December 21

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

Precipitation36.9 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: Peru, IL (11 mi away); precipitation: Utica Starved Rock Dam, IL (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

Cedar Point, IL · 6 mi

Granville, IL · 10 mi

613355b

Mc Nabb, IL · 11 mi

Illinois planting zones →

Questions about 61370

What planting zone is ZIP code 61370?

ZIP code 61370 (Tonica, 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 Tonica, IL?

The median last spring frost (32 °F) near 61370 is April 24; after May 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Peru station.

When is the first frost in Tonica, IL?

The median first fall frost near 61370 is October 18, giving a median frost-free growing season of 176 days.

When should I plant tomatoes in 61370?

Start tomato seeds indoors around Feb 27 – Mar 13 and set transplants outside around May 1 – May 15, one to three weeks after the median last frost.

How much rain and snow does 61370 get?

About 36.9 inches of precipitation a year (NOAA 1991–2020 normals, Utica Starved Rock Dam station).

How hot do summers get in Tonica, IL?

The average high peaks at 84 °F in July, with about 19 days a year at 90 °F or more.

What kind of soil does 61370 have?

The USDA soil survey maps Streator at the center of ZIP 61370: silty clay loam, poorly drained, pH about 7.0 (neutral).

Did spring come early in Tonica, IL in 2026?

Spring leaf-out near 61370 came on Mar 19 in 2026, 15 days earlier than the 1991–2020 average (Apr 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Tonica, IL?

Long-day onions: the longest day near 61370 is 15 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).