After a devastating flash flood swept through a popular hiking area in Grand Canyon National Park over the weekend, two people are confirmed dead and more than a dozen remain missing. The watershed burned during the Dragon Bravo Fire in July and August, causing increased risk of flash floods from heavy rain events. The monsoon season continues through Sept. 30, heightening danger in large swaths of Arizona, Utah and Colorado.

Mountains, steep hills, rocks, and clay soils produce rapid runoff, while recently burned areas pose high risk since burned soil can be water-repellent as pavement. Narrow canyons and slot canyons are particularly dangerous during inclement weather. Floods kill more people yearly than tornadoes, hurricanes or lightning.

Water levels can rise over 10 feet in minutes. To stay safe, check weather forecasts before hiking, avoid washes and low-lying areas during storms, and leave an itinerary with someone. Bring emergency communication devices and extra supplies.