If a flash flood is happening right now, move to higher ground immediately. Don’t wait to gather belongings, and don’t try to walk or drive through moving water. Just six inches of fast-moving floodwater can knock an adult off their feet. Your survival depends on getting above the water, not outrunning it.
Know the Difference: Watch vs. Warning
A flood watch means conditions could produce flooding. It’s your signal to prepare: charge your phone, locate important documents, and think about your route to higher ground. A flash flood warning means flooding is imminent or already happening. At that point, preparation time is over. If you’re in a flood-prone area, move to high ground right away.
Most phones receive Wireless Emergency Alerts automatically during a flash flood, with no app or signup required. These alerts use a distinct tone and vibration pattern, repeated twice, and they work even when cell networks are congested because they broadcast directly from nearby towers. If your phone is older or you want backup, a NOAA Weather Radio with tone alert will sound an alarm when warnings are issued for your area.
What to Do If You’re Indoors
Move to the highest floor of your building. Avoid basements and ground-level rooms, which can fill with water in minutes during a flash flood. If water is rising inside your home, do not touch electrical equipment or attempt to flip breakers while standing in water. If you can safely reach the main power switch from a dry location, turn it off. Otherwise, leave it alone and get to higher ground.
Stay inside unless the building itself is at risk of being swept away. A sturdy structure on higher ground is almost always safer than trying to travel through floodwater on foot.
What to Do If You’re Outdoors
Get to the highest ground you can reach. Move away from streams, drainage channels, canyons, and other low-lying areas. Flash floods often hit in places that aren’t near any obvious body of water, because runoff from higher terrain funnels into valleys and channels with tremendous force.
If you’re caught near rising water, climb. A hillside, a sturdy building’s upper floor, even a large rock formation is better than flat ground near a drainage path. Never attempt to cross flowing water on foot. Water that looks ankle-deep may be moving fast enough to sweep you downstream, and you can’t see what’s underneath: debris, open manholes, downed power lines.
Never Drive Through Floodwater
This is the single most important rule in a flash flood, and the one people break most often. The National Weather Service’s campaign puts it simply: turn around, don’t drown. Six inches of moving water can knock you down. Deeper water can float a vehicle and carry it off the road entirely. You cannot judge the depth of water covering a road, and you cannot see whether the road surface beneath it has been washed away.
If your car stalls in rising water, abandon it immediately and move to higher ground. Cars can be replaced. If water is rising around your vehicle and you can’t open the door, roll down the window (or break it) and climb out. Waiting for rescue inside a submerged vehicle is far more dangerous than getting wet.
What Floodwater Actually Contains
Floodwater is not just dirty rainwater. It routinely contains raw sewage from overwhelmed sewer systems, household and industrial chemicals, and bacteria that cause serious infections. In urban areas, it can carry hazardous waste including compounds like arsenic, chromium, and mercury from coal ash and industrial runoff. Downed power lines may be submerged and invisible.
Swallowing even a small amount of floodwater can cause diarrheal illness from bacteria like E. coli and Salmonella. Open wounds exposed to floodwater are at risk of infection, including from Vibrio bacteria in coastal areas, which can cause severe skin infections. If you have any cuts or scrapes and contact floodwater, wash the area with soap and clean water as soon as possible. Cover clean wounds with waterproof bandages. If you received a puncture wound or one contaminated with soil or sewage, you may need a tetanus booster.
The bottom line from the CDC: the best way to protect yourself is to stay out of the water entirely. If you must enter it, wear rubber boots, rubber gloves, and goggles. Wash your hands thoroughly after any contact, and always before eating. Wash children’s hands frequently, especially before meals.
Preparing Before Flood Season
Flash floods give little or no warning, so preparation matters more than with most disasters. A basic kit should include one gallon of water per person per day for several days, a battery-powered or hand-crank radio (ideally a NOAA Weather Radio), a whistle to signal for help, a cell phone with a backup battery, and local maps in case GPS is unavailable. Add moist towelettes, garbage bags with ties, soap, and hand sanitizer for sanitation when clean water isn’t available.
Know the elevation of your property relative to nearby streams and flood plains. Identify two routes to higher ground from your home and your workplace. If you live in a flood-prone area, keep important documents in waterproof containers and store them somewhere accessible on an upper floor.
Returning to a Flooded Home
After floodwaters recede, don’t rush back in. Return during daylight so you can see structural damage and hazards without needing to turn on electrical lights. Use battery-powered flashlights only, never candles or gas lanterns, because gas leaks are common in flooded buildings. If you smell gas when you enter, turn off the main valve, open all windows, leave immediately, and call your gas company or fire department. Don’t flip any switches or do anything that could create a spark.
If the house has been closed up for several days, open doors and windows and let it air out for at least 30 minutes before spending time inside. Assume mold is present in any home that has been flooded and sealed. Have an electrician inspect the electrical system before restoring power, and have your HVAC system professionally cleaned before turning it on, since ductwork can spread mold spores throughout the house.
Drying and Cleaning
Remove standing water with a wet-dry shop vacuum or sump pump, wearing rubber boots if the area is still damp. Set up fans at windows or doors blowing outward to push moist air out without spreading mold further inside. Dehumidifiers help pull remaining moisture from walls and flooring. The faster you dry the space, the less mold will establish itself.
Food and Water After Flooding
Throw away any food that may have contacted floodwater, any perishable food that lost refrigeration during a power outage, and anything with an unusual odor, color, or texture. Don’t take chances with canned goods that were submerged, since labels may be contaminated and seals may be compromised. If you have a private well, get it tested before using the water for anything. Until you’re confident your water is safe, use only bottled, boiled, or treated water for drinking, cooking, brushing teeth, washing dishes, making ice, and preparing baby formula.
Wash any clothes that contacted floodwater in hot water with detergent before wearing them again. Don’t bathe in rivers, streams, or lakes that may still be contaminated by flood runoff, even after the flood itself has passed.