Flash Flood and Storm Water in Your Home: Cleanup and Mold

Southern Nevada gets little rain, but when a monsoon thunderstorm hits, water can rush off dry desert ground toward low spots, and sometimes into garages, living rooms, and wall cavities. Outdoor floodwater is a different problem from a leaking supply line: federal health agencies treat it as contaminated. This guide covers staying safe, what to throw out, how to dry what’s left, how to document the damage, and when an independent mold check makes sense.

Why flash floods happen here

The National Weather Service office in Las Vegas explains that monsoon moisture typically arrives in July and August, setting off scattered thunderstorms that often form over the surrounding mountains and then move into the valley. The main hazard is heavy rain that triggers flash flooding, with water racing down normally dry washes or collecting in low-lying areas. The Clark County Regional Flood Control District likewise tells residents to expect sudden downpours and rapid flash flooding from July through September, “even on sunny days.”

When a storm is underway, the District’s advice is to stay inside and off the roads. Six inches of water can make a driver lose control, and a foot of water can float most cars. Turn around, don’t drown. A Flash Flood Warning from the National Weather Service means flash flooding is imminent or already happening; treat it as a signal to act now, not to go look.

Why outdoor floodwater counts as contaminated

Water that flowed across streets, yards, and storm drains before it reached your floor is not the same as water from a burst pipe. EPA warns that floodwater can carry microorganisms, including from sewage, along with chemical hazards, and CDC advises staying out of it because it can contain germs, chemicals, and other harmful material. That changes the cleanup: more materials have to go, protective gear matters more, and EPA says damage from sewage or other contaminated water is a job for a professional experienced with contaminated-water damage. If your situation was a single clean-water leak inside the house, see our guide to the first 48 hours after a water leak instead.

Safety before cleanup

  • Structural damage: CDC says not to go inside if there is obvious damage such as downed power lines or cracks in walls or the foundation, and to wait for a building inspector to confirm it’s safe.
  • Electricity: CDC says to shut off main power only if you can do it from a dry location, never to operate switches or use electrical equipment while standing in water, and to have an electrician check the system before turning power back on.
  • Gas: If you smell gas or suspect a leak, CDC’s guidance is to shut the main gas valve, open windows, leave immediately, and notify the gas company, police, or fire department. Don’t do anything that could make a spark.
  • Carbon monoxide: Never run a generator, pressure washer, or other gasoline engine indoors or in a garage. CDC says to keep them at least 20 feet from windows, doors, and vents.
  • Air it out: If the house has been closed up for several days, CDC suggests opening doors and windows for at least 30 minutes before staying inside for any length of time.

Protective gear

For mold cleanup after a flood, CDC recommends at least an N95 respirator, goggles, and protective gloves such as nitrile or rubber, plus rubber boots in wet areas. CDC also says people with asthma, lung disease, mold allergies, or weakened immune systems should stay away from the cleanup. If anyone develops symptoms, talk to a physician.

What to throw away

Both CDC and EPA advise removing materials that absorbed floodwater and can’t be thoroughly cleaned and dried. Porous materials commonly removed after flooding include:

  • Drywall and wall insulation that got wet
  • Carpet and carpet pad
  • Ceiling tiles
  • Mattresses and upholstery
  • Wallpaper and paper items
  • Food that came in contact with floodwater (CDC)

When in doubt, follow CDC’s rule: throw away anything that was wet with floodwater and can’t be cleaned and dried completely within 24 to 48 hours. Before anything goes to the curb, photograph it (see below).

EPA notes that older homes may have building materials containing asbestos or lead, which call for special precautions when disturbed during flood cleanup. EPA also says homes built before 1978 are more likely to have lead-based paint. If you’re unsure what a material is, have it evaluated before tearing it out.

Drying what remains

EPA notes that mold can grow on wood, drywall, carpet, and furniture that stay wet for more than 24 hours, and that everything needs to be completely dry before walls and floors are rebuilt. Practical points from EPA’s guidance:

  • If mold is already visible, gently clean it before turning on fans or dehumidifiers so the airflow doesn’t spread it.
  • If any part of your heating and cooling system was flooded, don’t run it to dry the house. Have it checked first.
  • Remove wet drywall and insulation so wall cavities can dry.
  • Never mix bleach with ammonia or other cleaners (CDC).

Our dry air helps, but water trapped under flooring, in bottom plates, or inside cabinets can stay wet long after the room feels dry. For more on hidden moisture, see moisture sources in Las Vegas homes.

Document for insurance and FEMA

FEMA’s National Flood Insurance Program recommends taking clear photos and video of damage before cleaning, repairing, or discarding anything, including water lines on walls, structural damage, and serial numbers of appliances. Keep small samples of carpet, drywall, or insulation, and save receipts.

Coverage details matter. FEMA says most homeowners policies do not cover flood damage, and mold damage is not covered under standard NFIP flood policies. Call your insurer or agent early. If a federal disaster declaration that includes Individual Assistance covers your area, FEMA says to file with your own insurer first, then apply at DisasterAssistance.gov or 1-800-621-3362. Our page on mold and homeowners insurance in Nevada covers the policy side.

Local resources

  • Clark County Regional Flood Control District: flash flood safety information, a real-time rainfall map, and an “Am I in a Flood Zone?” lookup.
  • National Weather Service Las Vegas: forecasts, watches, and warnings for Southern Nevada.

When to call professionals

Bring in qualified help when floodwater soaked large areas, reached wall cavities, or may have carried sewage; when the HVAC system took on water; or when anyone in the home is in a higher-risk group. EPA suggests looking for people with training or experience in water damage restoration and mold removal. See choosing a mold remediation contractor.

After cleanup and drying, an independent assessment can check whether moisture is gone and whether visible or hidden growth remains. Vegas Mold Pro does inspection and testing only, with no remediation, so we have no stake in the size of any repair. When sampling is useful, samples go to an independent AIHA-accredited lab and a written report typically follows within 24 hours. Learn how a mold inspection works or review our process.

Sources

Storm water got into your home?

Once the house is safe and drying is underway, we can check for remaining moisture and mold. Same-day appointments are often available, and flat pricing is quoted before you book. Call (702) 741-0666 or send a request.

Request an Inspection