ASK THE EXPERT
Ray O'Neil is the wilderness coordinator at Zion National Park.
"During the Southwest's late-summer monsoon season, clear morning skies are not a good indicator of flash flood danger. In fact, the surface heating they allow can lead to afternoon thunderstorms. Check the National Weather Service forecasts closely for the entire drainage of the canyon that you intend to enter, noting the chance of rain for the forecast area. Your safety is your responsibility. When in doubt, stay out."
Illustrations by Koren Shadmi