A severe thunderstorm sent visitors running for shelter at Zion National Park on Wednesday, July 29. The sudden storm arrived as the park entered one of its most unpredictable periods of the year for weather.
Zion’s monsoon season generally lasts from July through September. Clear morning skies can quickly give way to intense afternoon thunderstorms, heavy rain and dangerous flash floods.
The National Park Service is urging visitors to monitor conditions and prepare for weather that can change with little warning. The risk is especially serious inside the Narrows and Zion’s other slot canyons.
A storm does not have to be directly overhead to send fast-moving water rushing through a canyon. While it can be dangerous, if visitors take caution, they can see some beautiful rainbows after the storms pass.
Flash Floods Can Begin Miles Away
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Storms can form 15 to 20 miles upstream of Zion, meaning hikers may never see the rain that triggers an approaching flood. The Narrows receives water from a 288-square-mile watershed where rainfall can quickly funnel into the canyon.
Floodwater can carry rocks, tree limbs and other debris as it rises within seconds or minutes. Waterfalls may also appear along Zion’s cliffs during storms, but park officials warn that visitors should only watch them from a safe distance because falling water can carry debris.
Signs of a possible flash flood include thunder, building clouds, water suddenly turning muddy, floating branches, and the sound of rushing water farther up the canyon. Anyone who notices those warning signs should immediately move to higher ground.
According to Zion’s flash flood safety guidance, visitors cannot outrun a flash flood. Flooding can also occur even when sunny skies remain overhead.
Check Conditions Before Entering Any Canyon
Visitors should check the National Weather Service forecast, Zion’s current alerts, and the daily flash-flood potential before entering the Narrows or any other canyon. Conditions should also be checked for the specific trail or area being visited.
The Narrows closes whenever the National Weather Service issues a Flash Flood Warning. It remains closed for two hours after the warning is lifted.
Park officials recommend having a backup plan in case of storms. Alternatives include ranger talks, junior ranger programs, activities at the Nature Center, and evening programs at Zion Lodge.
Visitors should continue watching the weather throughout their trip and follow any closures or instructions issued by park rangers.