Flash Floods

This ephemeral waterfall near the Petroglyph Panel on State Route 24 is one of many fleeting cascades that can form after heavy rain.

NPS / E. Van Ness

Monsoon Season

From mid-June to mid-October, monsoon season brings heavy rain and thunderstorms to the Colorado Plateau. Storms may occur any time of day, but often increase in severity shortly after 12:00 pm, noon. Conditions can change rapidly and cell service is unreliable in most of the park, so check the weather before your visit, or go to the visitor center for current information.

Flash Floods

Less than one half inch of rainfall within an hour can cause a flash flood. Bare sandstone and scarce vegetation do little to soak up rain. Instead, muddy waterfalls cascade over the cliffs. Streams and rivers rise suddenly and may flood over their banks. Dry washes can fill with rushing water, several feet deep, carrying large rocks, logs, and debris.

 

This is one of three vehicles that was washed down Grand Wash in June of 2022. Two other vehicles were washed down Capitol Gorge during the same flood event.

NPS Photo / E. Van Ness

For Your Safety

Avoid Dangerous Areas

• Check the flash flood potential rating from the National Weather Service each day before visiting the park; weather predictions can change overnight. Current weather forecasts and WiFi are available at the visitor center.
• Avoid hiking and driving in canyons, gorges, and washes when there is a chance of storms. Even a slight chance of rain can produce a flash flood.
• Park in designated parking areas. Grand Wash and Capitol Gorge roads are in the bottom of canyons. Cars parked along the roadside can be swept away by floodwaters.
• Do not drive the Scenic Drive in heavy rain. Several paved dips along the Scenic Drive cross washes that can flood. Heavy machinery may be required to remove leftover mud and debris, leaving the 8-mile paved road impassable for hours or days.

 

Many paved and dirt roads in the park cross washes that are dangerous during flash floods.

NPS

 

Flooding has occurred on State Route 24, leaving rocks, mud, and debris on the roadway.

NPS / E. Van Ness

Pay Attention to Warning Signs

• Look for dark storm clouds. Storms to the west can cause flooding inside the park where no rain has fallen.
• Streams and rivers change color, becoming brown and muddy. They begin to rise and carry sticks and debris.
• Formerly dry washes start to flow with water.

During a Flash Flood

• Get to high ground immediately and wait for flooding to stop. Do not attempt to collect belongings. Water levels can rise rapidly.
• Flooding may last for 30 minutes to a few hours.
• Do not attempt to hike or drive through floodwater. Six inches of water can knock you off your feet. Flooding may increase dramatically before improving and can sweep cars away, smashing them into boulders and canyon walls.

 

Duration:

2 minutes, 45 seconds

The awesome power of flash floods and how to remain safe