Illinois Lawn Mowing Calendar
Published: February 1, 2026 · Updated: April 23, 2026
Illinois's continental climate varies significantly from north to south: Chicago experiences genuinely cold winters and short growing seasons while southern Illinois near Cairo has a transition-zone climate closer to Kentucky. Kentucky Bluegrass dominates the northern two-thirds, with Tall Fescue and even some warm-season grasses appearing in the southernmost counties.
Best Mowing Heights for Illinois Lawns
Kentucky Bluegrass
Ideal: 63mm (2.5")
Summer: 90mm (3.5")
Never below: 38mm
Mow every: 7 days (peak)
Tall Fescue
Ideal: 75mm (3.0")
Summer: 90mm (3.5")
Never below: 50mm
Mow every: 7 days (peak)
Zoysia Grass
Ideal: 38mm (1.5")
Summer: 45mm (1.8")
Never below: 13mm
Mow every: 14 days (peak)
Illinois Monthly Mowing Schedule
Based on Kentucky Bluegrass in zone 6a.
Mowing Tips for Illinois
The transition zone (zones 6–7) requires adjusting mowing height dramatically between seasons. Summer height should be 25–40mm higher than spring.
If you have Tall Fescue, maintain at 90mm through summer. This is higher than most guides suggest but critical for heat tolerance.
Never scalp warm-season grasses in fall transition. Leave at least 50mm to protect crowns entering dormancy.
What Makes Mowing in Illinois Different
Mowing in Illinois requires recognizing which climate zone your community falls within. Chicago and the northern third experience roughly a six-month mowing season from late April through October, with hard winters that kill off warm-season grass and favor Kentucky Bluegrass. Central Illinois (Peoria, Champaign, Springfield) has a slightly longer season and fewer extreme temperature swings, while southern Illinois near St. Louis-metropolitan East St. Louis and Cairo effectively operates as a transition zone where both warm- and cool-season grasses appear. For northern Illinois Bluegrass lawns, summer management is the defining challenge: July and August bring 32-35°C heat with significant humidity, pushing Bluegrass toward dormancy or disease pressure. Raise mowing height to 90mm by late May and maintain through August, accepting that the lawn will look slightly shaggy by late-summer standards. Chicago's heavy clay soils throughout the metro area compact severely under mowing traffic, particularly in the newer subdivisions built on disturbed construction fill; annual core aeration in September is essential for maintaining reasonable mowing conditions. Illinois farming soils in the central and southern portions of the state are among the richest agricultural soils in North America and provide excellent foundations for healthy lawns, though even good soils require proper management to avoid the compaction and drainage issues that affect every lawn to some degree.
Illinois Cities
Frequently Asked Questions
When should I start mowing my lawn in Illinois?
Start mowing in Illinois when grass shows active green growth and soil temperature exceeds 10°C. For zone 6a, this is typically March–April. Set mower at maximum height for the first 2–3 cuts.
What height should I mow Kentucky Bluegrass in Illinois?
Kentucky Bluegrass in Illinois should be maintained at 63mm during spring and fall, raised to 90mm in summer. Never cut below 38mm.
How often should I mow my lawn in Illinois in summer?
In Illinois's zone 6a climate, Kentucky Bluegrass typically needs mowing every 7–14 days in peak summer. If growth slows in heat, extend the interval.
When should I stop mowing my Illinois lawn in fall?
Cool-season grasses in Illinois can be mowed until the ground freezes — typically November. Final mow at 65mm.
Should I raise my mowing height in Illinois summers?
Yes — raising mowing height by 15–25mm in summer is one of the most important adjustments for Illinois lawns. Taller grass shades roots, retains soil moisture, and reduces heat stress. This applies to all grass types.