What Is a Storm Surge?

A surge of water can destroy a home faster than high winds. After the water recedes, hidden moisture lingers inside walls and basements, often leading to black mold. This scenario is common in coastal areas hit by hurricanes or in low-lying neighborhoods along rivers and canals. Knowing what a storm surge is—and how it causes damage—helps you protect your property before and after a storm.

The National Hurricane Center defines storm surge as “the abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tides.”

This rise in water level results from wind and low pressure driving water onto the coast. If a surge strikes at high tide, the combined storm tide can exceed 20 feet above the normal tide level, causing severe coastal flooding and widespread damage to buildings.

Storm surge vs. storm tide

• Storm surge: The wind- and pressure-driven rise above predicted tides.
• Tide: The regular rise and fall of sea level caused by gravity.
• Storm tide: Surge plus the tide at the same time.
• Inundation: The depth of water above normally dry ground during storm surge flooding.

This distinction matters for homeowners because forecasts may express water heights as either surge or inundation.

Why storm surge matters to Chicago and the Midwest

Chicago is inland, yet surge still matters. Here’s why:

• Coastal surge on the Atlantic and Gulf can move up rivers and canals for miles. That is how inland areas flood.
• Great Lakes storms can create surge-like water level spikes. People also call these seiches or setup. Wind can push water into bays, harbors, and river mouths.
• Once water enters basements and crawl spaces, the clock starts on mold growth. If materials stay wet beyond 24–48 hours, mold in drywall and mold in basements becomes likely.

After these weather systems pass through the Midwest, we see flooded basements, damaged sump systems, and wet structural wood. Rapid drying and mold remediation protect your home and health.

What causes storm surge?

Wind and pressure

The main driver is wind. Strong onshore winds from tropical storms and hurricanes push water toward the land. Low atmospheric pressure adds a small but significant lift.

Ocean floor and coastline shape

A wide, gently sloping continental shelf allows more water to build up, producing higher surge heights. Concave coasts and river mouths funnel water inland, increasing storm surge inundation.

Storm size and forward speed

A large storm covers a broader area, pushes on the ocean longer, and produces a bigger surge. The radius of maximum wind—the distance from the center to the strongest winds—is key. A faster-moving storm spikes water at the coast; a slower one pushes water farther inland.

Angle of approach

A perpendicular landfall is more damaging than an oblique track. This is why certain East Coasts locations experience worst case surges when storms hit straight on.

Storm surge vs. storm tide (easy comparison)

• Storm surge: Water rise from wind and pressure above the predicted tide.
• Tide: Regular rise and fall from moon and sun gravity.
• Storm tide: Surge plus the tide at that time.
• Inundation: Depth of water above ground level in a location.

How far inland can storm surge reach?

Even people far from beaches are at risk. Surge from hurricanes has been documented moving 15–25 miles inland along rivers and canals. Water can back up into basements, submerge cars, and damage critical systems like electrical panels and HVAC.

In Chicago and other Great Lakes cities, strong wind-driven water setup can create surge-like flooding in harbors and low-lying districts.

How experts predict storm surge

The National Hurricane Center uses the SLOSH model (Sea, Lake, and Overland Surges from Hurricanes) to estimate surge heights and worst-case inundation zones.

These maps show how far above ground level water may rise during surges from hurricanes. Homeowners can use them to plan evacuation routes and understand flood exposure.

Why storm surge is dangerous beyond the water line

Storm surge brings more than water:

• Structural force: Each cubic yard weighs about 1,700 pounds. Combined with waves, this can rip apart walls and decks.
• Erosion: Surge undermines foundations, highways, and protective dunes.
• Saltwater contamination: Salt and debris damage plumbing, soil, and vegetation.
• Mold risk: Flooded drywall, insulation, and wood start growing black mold within 24–48 hours without proper drying.

Events such as Hurricane Katrina and Hurricane Ian show how surge can devastate infrastructure even more than wind.

What to do before a storm surge

Make a simple plan

• Check if your home sits in a floodplain or near a river or canal.
• Save emergency numbers and insurance info to your phone.
• Set a family meeting point. Plan two routes in case one road is closed.

Protect your property

• Test your sump pump and install a battery backup.
• Clear gutters and downspouts. Extend downspouts 6–10 feet from the foundation.
• Elevate valuables, electronics, and important documents from the floor.
• Install check valves on drains where possible to reduce backflow.
• If you live near the lake or a river, consider low-profile barriers or sandbags for doorways and window wells.

What to do during a storm surge

• Follow local alerts. If officials issue an evacuation, go.
• Do not drive through floodwater, which is often deeper and faster than it looks.
• Keep kids and pets away from basements and low areas.
• Shut off power to flooded parts of the home if you can do it safely.
• Do not run generators or fuel-burning equipment indoors.

What to do after a storm surge

1: Stay safe

• Treat all floodwater as contaminated. Wear gloves, boots, and an N95 mask.
• Do not power on wet electrical systems. Have a licensed electrician inspect first.

2: Act fast to limit mold

• Pump standing water. Use wet vacs only if circuits are safe.
• Remove wet carpet, pad, and soggy drywall. Cut at least 12 inches above the water line.
• Run dehumidifiers and air movers. Vent to the outside.
• Dry the structure to target moisture readings before you rebuild.

3: Clean and disinfect

• Clean hard surfaces with detergent, then apply an appropriate antimicrobial.
• Discard porous items that stayed wet for more than 48 hours and cannot be cleaned.

4: Document for insurance

• Take photos and videos before and during work.
• Save receipts for pumps, drying equipment, and professional services.
• Keep a log of humidity and moisture readings if possible.

How Chicago Water & Fire Restoration helps

We began in 2012 with two team members. Today we have over 160 staff and more than 100 vehicles serving the Chicago Metropolitan area. We provide 24/7 emergency response for water removal, drying, and mold remediation.

Our process follows IICRC standards:

• Immediate inspection and moisture mapping.
• Rapid water extraction and containment.
• Drying to verified targets.
• Mold inspection and safe removal if needed.
• Build-back and documentation for your insurer.

Call 1-800-597-6911 for a free inspection and estimate. We’ll confirm your insurance coverage within an hour and begin work as soon as you approve.

FAQs

Is storm surge only a coastal problem?

No. Surge can push inland through rivers and canals. Great Lakes storms can also drive water into harbors and low-lying areas. Many inland homes flood this way.

How deep can storm surge get?

Depth varies by storm size, speed, track, and coastline shape. In major events, water can rise many feet above ground level and remain high for hours.

How soon does mold start after surge flooding?

Mold can start within 24–48 hours on wet porous materials. Act fast to remove water, lower humidity, and remove damaged materials.

Do I need professional help?

Call a professional if you have more than a small area of water damage, if contamination is likely, or if you cannot dry the structure within 48 hours. Professional teams have the equipment to extract water, control humidity, and verify dry-down.

Will insurance cover storm surge damage?

Coverage depends on your policy. Standard homeowners policies often exclude flood. Many claims involve sewer backup, sump failure, or wind-driven rain riders. We help you document the loss so your adjuster has what they need.

Need help today?

If your home flooded after a storm or lake surge, call Chicago Water & Fire Restoration at 1-800-597-6911. We offer 24/7 emergency service, free inspections, and fast water removal across the Chicago Metropolitan area. We will protect your property, reduce mold risk, and guide you through the next steps with clear, simple updates.

Storm surge brings water in fast. We get it out fast—so your home can dry, stay healthy, and get back to normal.