Flash Flood Warning: De Kalb, La Salle & Lee Counties IL — 2:12 AM–8:00 AM CDT

In the early morning hours of Sunday, September 20, 2026, the National Weather Service in Chicago issued a Flash Flood Warning for a wide stretch of north central Illinois, placing communities across southern De Kalb County, northern La Salle County, and Lee County under active flood threat. The warning took effect at 2:12 AM CDT and remains in force through 8:00 AM CDT, triggered by Doppler radar data confirming that severe thunderstorms had already dropped up to 3 inches of rain on the region, with rainfall rates between 1.5 and 2.5 inches per hour observed at the time of issuance.

Towns throughout the warning zone — including Sandwich, Mendota, Amboy, Sheridan, Shabbona, Hinckley, Somonauk, Earlville, Waterman, Leland, Paw Paw, and Sublette — face ongoing and developing flash flood conditions as of this publication. NWS Chicago warns that an additional 1 to 3 inches of rain is still possible within the warned area, meaning conditions may worsen before the warning expires. Residents near creeks, streams, low-lying roadways, underpasses, and areas with poor drainage should treat this warning as active and take precautions accordingly.

What the National Weather Service Confirmed

The Flash Flood Warning was issued by NWS Chicago at 2:12 AM CDT on Sunday, September 20, 2026. The warning covers three counties in north central Illinois:

• Southern De Kalb County
• Northern La Salle County
• Lee County

According to NWS Chicago, Doppler radar indicated that thunderstorms produced up to 3 inches of rain across the warned area, with rainfall rates measured at 1.5 to 2.5 inches per hour — rates capable of overwhelming storm drains and drainage infrastructure within minutes, rapidly raising water levels in waterways throughout the region.

NWS Chicago reported that flash flooding was either already ongoing or expected to begin shortly across multiple terrain types and infrastructure, specifically including:

• Creeks and streams
• Drainage ditches
• Streets and roadways
• Underpasses
• Low-lying areas
• Other areas with poor drainage

An additional 1 to 3 inches of rainfall remained possible within the warned area at the time of issuance, with total accumulations potentially reaching significant levels before conditions improve. The Flash Flood Warning is valid through 8:00 AM CDT.

What Homeowners in Affected Towns Should Check Now

Once the storm passes and it is safe to go outside, a prompt property inspection can help you identify damage before moisture migrates into walls, insulation, or structural components and becomes a larger, costlier problem. Homeowners in Sandwich, Mendota, Amboy, Sheridan, Shabbona, Hinckley, Somonauk, Earlville, Waterman, Leland, Paw Paw, and Sublette — and throughout the surrounding communities in De Kalb, La Salle, and Lee counties — should walk through the following checklist as soon as conditions allow.

Roof

• From the ground, scan for missing, lifted, or visibly creased shingles
• Check for displaced ridge caps or exposed underlayment
• Inspect around skylights, chimneys, and vent stacks for loose or shifted flashing
• If your attic is safely accessible, look for daylight penetration or water staining on the roof decking

Gutters and Downspouts

• Clear any debris — leaves, twigs, shingle granule buildup — that could be blocking drainage
• Confirm downspout extensions are intact and directing water well away from the foundation
• Check whether gutters have pulled away from the fascia board under the weight of accumulated water
• After rain ends, watch for pooling water near the foundation line

Siding and Exterior

• Walk the full perimeter and look for buckled, cracked, or water-stained siding panels
• Check caulk lines around windows and exterior doors for separation or visible gaps
• Look for soil erosion or displaced mulch against the foundation — these can channel water toward the structure rather than away from it

Trees and Landscaping

• Check for hanging or partially downed limbs over the roof, driveway, or power lines
• Look for root upheaval or any notable lean in trees near the foundation or utility easements
• Do not attempt to remove large limbs yourself — contact a licensed and insured tree service

Interior Water Intrusion

• Check basements and crawlspaces for standing water or seepage along walls and floor joints
• Inspect window wells — overflowing window wells are among the most common and preventable sources of basement flooding following heavy rain events
• Examine interior ceilings and upper walls for new water stains, bubbling paint, or areas of soft or damp drywall
• Check around water heaters, sump pumps, and floor drains for signs of backup or overflow

If your sump pump ran overnight, verify it is still functioning properly and that the discharge line is unobstructed. Extended rain events can overwhelm even a working pump when the discharge area is itself flooded — a situation that becomes more common with multi-inch rainfall totals like those reported tonight across De Kalb, La Salle, and Lee counties.

If You Find Damage

Safety comes first. Do not wade through standing water indoors or outdoors. Floodwater can conceal hazards including downed electrical lines, open drains, displaced debris, and structural undermining that is not visible on the surface. If your home has experienced significant water intrusion, turn off electricity to affected areas at the breaker panel before entering, and contact a qualified professional before beginning any work.

Once you can safely move through your property, document everything before you clean up or move anything. Use your phone to capture wide-angle and close-up photos and video of every affected area — roofline, ceilings, walls, flooring, mechanical equipment, and personal property. Detailed documentation from the hours immediately following a storm is one of the most valuable tools you have when working through an insurance claim.

Practical next steps if you identify storm or flood damage:

1. Contact your insurance company to open a claim promptly. Most policies have notice requirements, and timely reporting protects your coverage options.
2. Make temporary protective measures where safe — placing buckets under active roof leaks, covering broken windows with plastic sheeting — but do not undertake permanent repairs before an adjuster has inspected the damage.
3. Keep every receipt for emergency materials or services you pay for out of pocket, including any hotel stays if you are displaced.
4. Schedule a professional inspection with a licensed restoration contractor who can document the full scope of damage and provide a detailed written estimate for review by your insurer.

Allied Emergency Services is an Illinois-licensed restoration contractor (IL License #104.019029), founded in 2015 and active in the Greater Midwest through more than a decade of storm damage restoration work. Our team can perform a thorough on-site property inspection, produce a detailed and itemized repair estimate, and meet with your insurance adjuster on-site to walk through the documented scope of damage. As a licensed restoration contractor, Allied does not negotiate, settle, or adjust insurance claims on your behalf — but we make certain the scope of your damage is fully and accurately documented, and that every repair is completed to code. Learn more about how we help homeowners navigate the process at Allied Emergency Services Storm Damage Restoration.

This article is provided as general information only and does not constitute legal or insurance advice. Every claim situation is unique; consult your insurance policy and a licensed professional for guidance specific to your circumstances.

Contact Allied Emergency Services — Available 24/7

If you are in Sandwich, Mendota, Amboy, Sheridan, Shabbona, Hinckley, Somonauk, Earlville, Waterman, Leland, Paw Paw, Sublette, or anywhere across De Kalb, La Salle, or Lee County and you have discovered damage from tonight’s flash flood event, Allied Emergency Services is ready to respond.

We operate 24 hours a day, 7 days a week — because storms don’t keep business hours, and the consequences of waiting on water damage can compound quickly.

• Call us: (800) 792-0212
• Text ESTIMATE to: (844) 907-2546

Our experienced restoration teams serve communities across the Greater Midwest. Whether you have found a compromised roof, water in your basement, or you simply aren’t sure what the storm left behind, we will give you a straight assessment — and get to work. Visit our storm damage restoration page for more on how Allied helps homeowners move from inspection through completed, code-compliant repairs.