Updated daily

Illinois soil temperature

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Estimated 2–4 inch soil temperature, statewide average . Based on NOAA weather stations near representative Illinois locations.

Check your exact ZIP

Enter your ZIP code for the estimated soil temperature near you, plus what it means for seasonal pre-emergent timing. Use the separate tools below for other lawn tasks.

What this soil temperature means for your Illinois lawn

The Illinois reading loads from the latest daily data. Use the value above or enter your ZIP code for a location-specific recommendation.

Estimated soil temperature at Illinois locations

ZIP code Est. soil temp Data through
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Values load from each ZIP's nearest NOAA station in the current R2 snapshot. Enter your own ZIP above for a reading closer to home.

Nearly 400 Miles of Spring: The Illinois North-South Gap

Illinois stretches from Wisconsin to the latitude of Virginia, and soil temperature shows it. Carbondale and the southern tip typically hold 55°F at lawn depth by late March or early April, while Chicago and Rockford wait until mid-to-late April. That two-to-three week spread means there is no single answer to when Illinois soil is ready; the answer depends on where you stand along Interstate 57.

Springfield and Champaign in central Illinois split the difference, usually crossing in mid-April. The state's flat terrain makes the gradient unusually clean compared with hillier states: on an Illinois soil temp map, the isotherms march north in orderly bands through April, and your position in that band matters more than any calendar date.

Prairie Soil, Lake Michigan, and the Chicago Heat Island

Two local effects complicate the clean gradient. First, Lake Michigan: cold lake water chills the shoreline through spring, so lakefront neighborhoods in Chicago and the North Shore warm a few days behind the western and southern suburbs. Second, the urban heat island works the other way, with dense city blocks holding overnight warmth that nudges soil temperatures up compared with rural collar counties.

Downstate, the dark prairie-derived soils that make Illinois a farming powerhouse absorb solar radiation efficiently, but they are also deep and often wet in spring. A saturated April can hold soil temperature in Illinois down for a week or more after air temperatures turn warm, which is why University of Illinois Extension emphasizes checking soil readings before fieldwork and lawn treatments alike.

The 50-Degree Rule: Lawns and Corn Share a Threshold

Illinois is corn country, and the agronomy overlaps neatly with lawn care. Corn planting traditionally waits for soil at 50°F and rising, the same neighborhood as the thresholds that drive spring lawn work. When you see planters rolling in the fields outside town, your lawn soil is usually within days of the readings that matter for turf.

Garden timing follows the same ladder: peas and lettuce go in around 45°F, sweet corn and beans at 50-55°F, and tomatoes and peppers once soil holds 60°F, which usually means mid-May in Chicago and late April in far southern Illinois. Checking the lawn soil temperature for Illinois on this page covers all three uses at once.

How Illinois compares to the rest of the country

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Estimated 2–4 inch soil temperature by state . Tap a state for its detailed page.

About Illinois lawns

Illinois is in USDA Hardiness Zones 5a-7a, with a cool-season lawn climate. Common grass types include Kentucky Bluegrass, Tall Fescue, Perennial Ryegrass, Fine Fescue.

These estimates are modeled from air temperature (about ±5°F at 2–4 inch depth — methodology). For local agronomic guidance, see the University of Illinois Extension.

Common Illinois soil temperature questions

What is the current soil temperature in Illinois?

This page shows a statewide estimated 2–4 inch soil temperature for Illinois, recomputed daily from NOAA weather station records, plus per-ZIP estimates for representative Illinois locations. Enter your ZIP code for the reading nearest you.

At what soil temperature should I apply pre-emergent in Illinois?

Apply pre-emergent when Illinois soil temperatures approach 55°F at a 2–4 inch depth in spring — crabgrass germinates as soil holds 55°F and above. In Illinois that typically happens mid-april to early may.

What soil temperature does grass seed need in Illinois?

Soil temperature alone does not set a seeding date. Seeding timing for common Illinois lawns (Kentucky Bluegrass, Tall Fescue, Perennial Ryegrass, Fine Fescue) follows published regional calendars for each grass type; the overseeding tool shows any calendar available for your ZIP, with this estimate as context.

How accurate is this Illinois soil temperature estimate?

It is modeled from air temperatures with a published lag model, not measured by in-ground sensors, and is typically within about ±5°F at 2–4 inch depth. Shade, moisture, and snow cover shift real readings; for precise numbers use a soil thermometer or University of Illinois Extension resources.

How much earlier does southern Illinois soil warm than Chicago?

Typically two to three weeks. Carbondale, Marion, and the southern tip often hold 55°F at 2-4 inches by late March or the first days of April, while Chicago-area lawns usually get there in mid-to-late April. The gap tightens in fast, warm springs and stretches in cold ones, but southern Illinois always leads.

Does Chicago's urban heat island affect soil temperature?

Yes, modestly. Pavement and buildings hold overnight heat, so soil in the city core can run a few degrees warmer than in outlying suburbs, partially offsetting the cooling effect of Lake Michigan near the shore. The net result: city lawns away from the lakefront often cross spring thresholds slightly before both the North Shore and the rural collar counties.

What soil temperature do Illinois farmers wait for before planting corn?

The standard agronomic rule is 50°F at planting depth and trending upward, since corn seed germinates poorly and risks rot in colder soil. Central Illinois soils typically reach that in mid-April. For home gardeners the same benchmark works for sweet corn and beans, while warm-season crops like tomatoes want another 10 degrees on top of it.

Soil temperature in nearby states

AlaskaConnecticutDelawareIndianaIowa

View the national soil temperature map