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How can I avoid getting caught in a flash flood?

Dr. Colin Little

Dr. Colin Little

MD, FAWM, Chief Medical Officer, GOES Health

The short answer

To avoid getting caught in a flash flood, check the forecast for where you're going and for the land upstream, treat a Flash Flood Warning as an order to reach higher ground, never drive or walk into water on a road, and don't camp in a dry wash or canyon bottom when rain is possible anywhere upstream. Flash floods can come from rain you never see.

Don't judge flash flood risk by the sky over your head. Most flash floods start with heavy thunderstorm rain that falls faster than the ground can soak it up.1 It runs to the lowest ground, often a canyon or dry riverbed, and rain from miles around arrives in one channel at once.2 The storm can be several miles upstream, so a dry wash can flood under sunny skies.2 Once the water reaches you it rises within minutes, and you can't outrun it.3

Check the forecast for where you'll be and for the country upstream.4 A Flash Flood Watch means conditions are right for flooding, so be ready to move.5 A Flash Flood Warning means a flash flood is happening or about to happen. Move to higher ground immediately.5 Keep phone alerts on, but don't rely on them: only the most dangerous warnings buzz a phone, and canyons often have no signal.67 A NOAA weather radio picks up every warning.8 In canyon country, summer storms often turn severe after noon, so finish canyon hikes in the morning.4

More than half of flood drownings happen when someone drives into floodwater.9 The water is deeper than it looks, the engine stalls, and moving water lifts the vehicle and carries it off with everyone inside.10 Six inches of fast-moving water can knock an adult over, twelve inches can carry away most cars, and two feet can carry away an SUV or a pickup.9 You can't judge the depth or see whether the road underneath has collapsed, least of all at night.9 Treat any water on the road as too deep, and never drive around a barricade.9 If water rises around your car, leave it for higher ground if you can do so safely.11

Camped or hiking, pick your ground before the rain does. Never camp in a dry wash.11 If you must camp near one, get as high as you can and check for stains and debris lines from past floods.12 Before camping or heading down a canyon, know the nearest way up.12 Building clouds, thunder, a stream turning muddy, floating sticks, rising water, or a roar upstream all mean a flood is coming.3 Climb at once: even a few feet higher can save your life.3 Don't stop for gear or try to outrun it downstream.3 Don't wade across moving floodwater, since six inches of fast-moving water can knock you off your feet.11 Then stay high; the water can take hours to drop.3

Sources

  1. [1] Flash Flooding Definition (NWS Philadelphia/Mount Holly). Accessed September 17, 2026. https://www.weather.gov/phi/FlashFloodingDefinition
  2. [2] Flood Related Hazards (NOAA National Weather Service). Accessed September 17, 2026. https://www.weather.gov/safety/flood-hazards
  3. [3] Flash Floods (Zion National Park, NPS). Accessed September 17, 2026. https://www.nps.gov/zion/planyourvisit/flash-flood.htm
  4. [4] Monsoon Season (NPS Articles). Accessed September 17, 2026. https://www.nps.gov/articles/monsoon-season.htm
  5. [5] Flood Watch vs. Warning (NOAA National Weather Service). Accessed September 17, 2026. https://www.weather.gov/safety/flood-watch-warning
  6. [6] Weather warnings on the go! Wireless Emergency Alerts (NWS). Accessed September 17, 2026. https://www.weather.gov/wrn/wea
  7. [7] Flash Floods (Capitol Reef National Park, NPS). Accessed September 17, 2026. https://www.nps.gov/care/planyourvisit/flash-floods.htm
  8. [8] Changes to the Wireless Emergency Alerts for Flash Flood Warnings (NWS Honolulu). Accessed September 17, 2026. https://www.weather.gov/hfo/WEAFloodChange
  9. [9] Turn Around Don't Drown (NOAA National Weather Service). Accessed August 21, 2026. https://www.weather.gov/safety/flood-turn-around-dont-drown
  10. [10] Floods: Things to Know (USGS Water Science School). Accessed September 17, 2026. https://www.usgs.gov/special-topics/water-science-school/science/floods-things-know
  11. [11] Turn Around Don't Drown (NWS Tulsa). Accessed September 17, 2026. https://www.weather.gov/tsa/hydro_tadd
  12. [12] Weather Dangers (Grand Canyon National Park, NPS). Accessed September 17, 2026. https://www.nps.gov/grca/planyourvisit/weather-dangers.htm

About the author

Dr. Colin Little

Dr. Colin Little

MD, FAWM, Chief Medical Officer, GOES Health

  • Board Certified Emergency Physician
  • Fellow of the Academy of Wilderness Medicine (FAWM)
  • Wilderness Medicine Fellowship, University of Utah
  • Emergency Medicine Residency and Chief Resident, Stanford / Kaiser
  • Doctor of Medicine, University of Arizona College of Medicine – Phoenix
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