NWS Issues Severe Thunderstorm Warning for McHenry, De Kalb, Boone Counties IL

On the afternoon of Thursday, August 21, 2026, the National Weather Service in Chicago issued a Severe Thunderstorm Warning for parts of three northern Illinois counties — northern De Kalb County, southwestern McHenry County, and southern Boone County — as a fast-moving storm system tracked southeast across the region. The warning went into effect at 2:17 PM CDT and was set to expire at 3:00 PM CDT, placing communities including DeKalb, Sycamore, Genoa, Cortland, Kirkland, Maple Park, Kingston, and Fairdale directly in the path of a confirmed severe weather event.

Radar tracked the storm over Kirkland — approximately 7 miles west of Genoa — at the time of issuance, moving southeast at 25 miles per hour. NWS Chicago confirmed radar-indicated hazards of 60 mph wind gusts and quarter-size hail measuring 1.00 inch in diameter. For homeowners across this corridor, that combination of wind and hail is exactly the kind of event that warrants a careful post-storm inspection of roofs, siding, gutters, and trees in the days that follow.

What the National Weather Service Confirmed

The warning was issued by the National Weather Service office in Chicago, the federal agency responsible for official weather forecasting and severe weather alerts across northern Illinois. The warning was based on radar evidence — not a spotter report — meaning the storm had already developed the characteristics of a severe thunderstorm by the time the alert reached the public.

Here is what NWS Chicago officially confirmed for this event:

• Warning issued: August 21, 2026 at 2:17 PM CDT
• Warning expired: 3:00 PM CDT
• Storm location at issuance: Over Kirkland, 7 miles west of Genoa
• Storm motion: Southeast at 25 mph
• Wind hazard: Radar-indicated gusts up to 60 mph
• Hail hazard: Quarter size — 1.00 inch in diameter — radar-indicated
• Counties under warning: Northern De Kalb County, southwestern McHenry County, and southern Boone County
• Affected communities listed by NWS: DeKalb, Sycamore, Genoa, Cortland, Kirkland, Maple Park, Kingston, and Fairdale

NWS stated that the primary expected impacts from this storm system included hail damage to vehicles and wind damage to roofs, siding, and trees. Quarter-size hail — at one inch in diameter — is large enough to dent aluminum gutters and cause surface damage to asphalt shingles. Wind gusts in the 60 mph range exceed the designed wind resistance of many standard residential roofing systems, particularly on older homes where shingles may already be weathered or inadequately fastened. For the current NWS forecast and any follow-up statements, visit weather.gov.

What Homeowners in DeKalb, Sycamore, Genoa, and Surrounding Communities Should Check Now

If you live in DeKalb, Sycamore, Genoa, Cortland, Kirkland, Maple Park, Kingston, Fairdale, or anywhere along the storm’s southeast track, a methodical exterior inspection makes sense before the next rain event moves through. Catching storm damage early — and documenting it properly — protects both your home and your ability to file a timely insurance claim if one is warranted.

Here is what to look for:

Roof

• From the ground, scan for missing, lifted, or curled shingles — 60 mph gusts can cause shingle uplift, especially on roofs that are several years old or where fasteners have begun to loosen
• Look for dark bruising, circular dimpling, or impact patterns across shingle surfaces — these are the hallmarks of hail strikes and can be easy to miss until water begins to penetrate
• Pay close attention to ridge caps, flashing around chimneys, and pipe boot seals — these details fail first in high-wind events and are the most common entry points for water
• Do not walk your roof if it is wet or if you are unsure of your footing; ground-level observation with binoculars is a safer starting point

Siding and Exterior Trim

• Quarter-size hail can dent aluminum siding and crack or fracture vinyl; look for circular impact patterns running across exposed panels in a consistent pattern
• Inspect wood fascia boards, soffit, and exterior trim for splitting or cracking from wind-driven debris
• Check window screens and frames for tears, dents, or displaced glazing

Gutters and Downspouts

• Hail impact on aluminum gutters leaves distinct, rounded dents — one of the most reliable ground-level indicators that hail actually reached your property rather than dissipating before arrival
• Look for displaced downspout extensions and check that gutter hangers are still secure after the wind loading the storm brought through

Trees and Overhanging Branches

• Note any broken or hanging limbs, particularly near or above your roofline — storm-weakened branches can drop onto the structure in subsequent wind events
• Look for bark stripping on tree trunks facing the storm’s direction of travel, a common side effect of wind-driven hail on exposed wood surfaces

Interior — Signs of Water Intrusion

• If you can safely access your attic, check for signs of water, daylight where there should be none, or displaced insulation near the eaves and ridge
• Inspect ceilings and upper walls in rooms directly below the roofline for water staining, bubbling paint, or soft spots that were not there before the storm

Photograph everything you observe before touching or cleaning anything. Date-stamped images from your phone are straightforward records that matter in any subsequent insurance discussion.

If You Find Damage

If your inspection turns up credible signs of storm damage — hail marks on gutters, missing or displaced shingles, cracked siding panels — here is a practical sequence of next steps:

1. Document before you do anything else. Walk the full exterior perimeter and photograph all visible damage from ground level. Note the date and time of your inspection. Take photos from multiple angles and capture wide shots alongside close-ups. These records matter for any insurance conversation that follows.
2. Notify your insurance company. Contact your insurer to report the event and ask about the claims process under your specific policy. Most standard homeowner policies cover sudden storm damage, but timelines for reporting and the documentation required vary by carrier. Your insurer will assign an adjuster to evaluate the property.
3. Have a licensed restoration contractor conduct a professional inspection. A qualified contractor can safely assess areas that are difficult or unsafe for a homeowner to inspect firsthand, prepare a detailed written estimate of the work required, and be available on-site when your insurance adjuster visits. Allied Emergency Services documents damage thoroughly, provides scope-of-repair estimates, and performs covered restoration work — but does not negotiate, settle, or adjust insurance claims on a homeowner’s behalf; that role belongs to your adjuster and, if applicable, a licensed public adjuster.
4. Be selective about who you hire. After any significant NWS-warned severe weather event, unlicensed contractors and out-of-state crews sometimes move through affected neighborhoods soliciting door-to-door work. In Illinois, roofing contractors are required to hold an active state license. Ask for credentials and verify them before signing any contract or providing a deposit.

Allied Emergency Services has worked in storm damage restoration across northern Illinois for 27 years, holding an active Illinois Roofing Contractor license. Our team is familiar with the De Kalb, McHenry, and Boone County markets and has assisted homeowners and commercial property owners through thousands of storm-related assessments and repairs. For general emergency preparedness guidance before, during, and after severe weather, ready.gov is a reliable federal resource.

Schedule a Free Inspection

If your home or commercial property sits along the track that crossed northern De Kalb County, southwestern McHenry County, or southern Boone County on Thursday afternoon — and you want a professional assessment before deciding whether to file a claim — Allied Emergency Services is available around the clock.

A no-obligation inspection gives you an accurate picture of your property’s actual condition, documented in writing, so you can make an informed decision about next steps. That is the right first move after a confirmed severe weather event, regardless of what it ultimately leads to.

Visit our storm damage restoration page to learn more about how we work, or reach us directly:

• Call 24/7: (800) 792-0212
• Text ESTIMATE to (844) 907-2546 to request a callback at your convenience

This article is provided as general public information following a confirmed NWS severe weather event and does not constitute legal, financial, or insurance advice. For guidance specific to your policy or claim, consult a licensed insurance professional.