The current average 2-inch soil temperature across Illinois is 77°F. Readings range from 73°F to 80°F, from 3 USDA and NOAA monitoring stations. Soil across Illinois is running 3°F above the seasonal normal of 73°F for mid-August, based on 3 of 3 stations with historical records. Illinois spans USDA hardiness zones 5b to 7a, cool-season grass country. Last updated August 16, 2026.
Summer conditions across Illinois with soil averaging 77°F at 2 inches. Warm-season grasses are in peak growth; keep cool-season lawns mowed high and watered deep. The next application windows arrive in fall, starting with pre-emergent as soil falls back through 70°F.
For cool-season lawns (fescue, bluegrass, ryegrass), fall is the best time to plant grass seed in Illinois, with spring the second choice: fall seedlings face less weed competition and mature before summer heat. The window opens as 2-inch soil falls back through 70°F, and germination slows sharply once soil drops below 50°F, typically around November 1.
Spring is the second choice: the window opens when soil first holds 50°F and narrows as soil passes 65°F, typically by May 18.
Fall seeding also needs a stop date: new seedlings want about six weeks of growth before frost arrives. Your city page estimates the last safe seeding date from its nearest station: see when to plant in Chicago, when to plant in Springfield or when to plant in Peoria. Readings current through August 16, 2026: Illinois averages 77°F at 2 inches right now; the Current Planting Conditions section above reads that number against the season.
Typical dates are computed from historical 2-inch soil temperature averages at 3 monitoring stations in Illinois; your own window depends on your nearest station's readings.
Historical 2-inch soil temperature normals for Illinois: the median across 3 in-state stations with multi-year records. Any given year runs ahead of or behind these values; the live average at the top of this page shows where this year stands.
| Month | Average 2-inch soil temperature |
|---|---|
| January | 33°F |
| February | 34°F |
| March | 44°F |
| April | 54°F |
| May | 64°F |
| June | 74°F |
| July | 77°F |
| August | 76°F |
| September | 70°F |
| October | 58°F |
| November | 44°F |
| December | 38°F |
Grass seed germination
Grass seed germination temperatures across Illinois. Soil warmth varies by location, so check a city page for the live reading and what germinates there now.
| Grass species | Seeding soil temp (2 in) | Days |
|---|---|---|
| Kentucky bluegrass | 50–65°F | 14-30 |
| Tall fescue | 50–65°F | 7-12 |
| Perennial ryegrass | 50–65°F | 5-10 |
| Fine fescue | 50–65°F | 7-14 |
| Bermudagrass | 75–90°F | 10-30 |
For root-zone timing (fertilizer, aeration, weed control), see the 4-inch soil temperature for Illinois. For accumulated-heat timing, see growing degree days for Illinois. For how wet the ground is versus normal, see soil moisture for Illinois. See the Illinois soil temperature map for the full station view.
Interpolated from the latest 4-inch readings and refreshed daily.
| Station | 2" Temp | Last Reading |
|---|---|---|
| Mason #1 (Mason) | 78°F | 2026-08-16 |
| Champaign 9 SW | 80°F | 2026-08-16 |
| Shabbona 5 NNE | 73°F | 2026-08-16 |
| City | ZIP | Current Temp |
|---|---|---|
| Arlington Heights | 60004 | 73°F |
| Aurora | 60502 | 73°F |
| Barrington | 60010 | 73°F |
| Belleville | 62220 | 82°F |
| Bensenville | 60105 | 73°F |
| Bloomingdale | 60108 | 73°F |
| Bloomington | 61701 | 80°F |
| Bolingbrook | 60440 | 73°F |
| Carbondale | 62901 | 80°F* |
| Carol Stream | 60116 | 73°F |
| Champaign | 61820 | 80°F |
| Chicago | 60290 | 73°F |
| Chicago Heights | 60411 | 73°F |
| Crystal Lake | 60012 | 73°F |
| Danville | 61832 | 80°F |
| Decatur | 62521 | 80°F |
| Des Plaines | 60016 | 73°F |
| Downers Grove | 60515 | 73°F |
| East Peoria | 61611 | 78°F |
| East Saint Louis | 62201 | 82°F |
| Edwardsville | 62025 | 80°F |
| Elgin | 60120 | 73°F |
| Elk Grove Village | 60007 | 73°F |
| Evanston | 60201 | 73°F |
| Fox Valley | 60597 | 73°F |
| Galesburg | 61401 | 78°F |
| Glen Ellyn | 60137 | 73°F |
| Glenview | 60025 | 73°F |
| Hinsdale | 60521 | 73°F |
| Hoffman Estates | 60169 | 73°F |
| Jacksonville | 62650 | 78°F |
| Joliet | 60431 | 73°F |
| Libertyville | 60048 | 73°F |
| Loves Park | 61111 | 73°F |
| Mascoutah | 62224 | 82°F |
| Mchenry | 60050 | 73°F |
| Melrose Park | 60160 | 73°F |
| Moline | 61265 | 73°F* |
| Naperville | 60540 | 73°F |
| Normal | 61761 | 80°F |
| North Chicago | 60064 | 73°F |
| Northbrook | 60062 | 73°F |
| Oak Lawn | 60453 | 73°F |
| Oak Park | 60301 | 73°F |
| Orland Park | 60462 | 73°F |
| Palatine | 60038 | 73°F |
| Pekin | 61554 | 78°F |
| Peoria | 61601 | 78°F |
| Plainfield | 60544 | 73°F |
| Quincy | 62301 | 80°F |
| Rock Island | 61201 | 72°F* |
| Rockford | 61101 | 73°F |
| Saint Charles | 60174 | 73°F |
| Schaumburg | 60159 | 73°F |
| Skokie | 60076 | 73°F |
| Springfield | 62701 | 78°F |
| Tinley Park | 60477 | 73°F |
| Urbana | 61801 | 80°F |
| Waukegan | 60079 | 73°F |
| West Chicago | 60185 | 73°F |
| Wheaton | 60187 | 73°F |
| Wood Dale | 60191 | 73°F |
Modeled estimate where no monitoring station is within 75 miles; all other readings are measured at USDA and NOAA stations.
Fall is the best time to overseed a thin lawn.
Core aeration relieves compaction, but timing decides whether the lawn recovers in a week or struggles for a month.
Brown patch and Pythium strike when humid nights hold above 68°F on lush, over-fertilized turf; dollar spot, red thread, and rust hit slow-growing lawns at 60-85°F.
Check whether your soil is warm enough for the seed you bought: cool-season grass seeds into 50-65°F soil (tall fescue prefers 60°F and up), warm-season into 75-85°F.
The current average 2-inch soil temperature across Illinois is 77°F. Readings range from 73°F to 80°F depending on location and elevation, from 3 USDA and NOAA monitoring stations. Soil across Illinois is running 3°F above the seasonal normal of 73°F for mid-August, based on 3 of 3 stations with historical records.
Apply pre-emergent herbicide when soil at 2 inches reaches 55°F for several consecutive days. Timing varies across Illinois, so check your city's page for station-specific readings and the pre-emergent timing recommendation.
Illinois spans USDA hardiness zones 5b to 7a, cool-season grass country. For cool-season grasses (fescue, bluegrass), the fall window typically opens around September 8 and the spring window around March 30, based on historical 2-inch soil temperature averages at 3 in-state stations. Timing varies by location, so check your city's planting window for the dates specific to your area.