Monsoon season bringing death and destruction to national parks around Southwest

As the desert southwest shifts into monsoon season, unpredictable flash floods are wreaking havoc in and around the region's national park sites, prompting closures and causing at least five deaths last week. 

Zion National Park in Utah announced a closure of all slot canyons, including the popular Narrows hike, over fears of flash flooding, while close to two dozen visitors at Black Canyon of the Gunnison National Park in Colorado were trapped by mudslides that buried a road beneath several feet of debris. Five members of a family were also killed just outside Capitol Reef National Park after getting caught in a flash flood while hiking. 

Monsoon season in the southwest typically runs from June 15 to the end of September, peaking through July and August. During a monsoon, large thunderstorms can form rapidly, dumping large amounts of rain in a short amount of time. This year, the North American monsoon seasonal forecasts are predicting above-average precipitation, which may provide short-term relief for a drought-stricken region even as it increases the likelihood of deadly flash floods. 

Such floods have been made worse by an aggressive fire season, with a dozen large fires currently burning across Colorado, Utah, New Mexico, Arizona and Nevada. Fires can denude entire forests, and soils that have been scorched are less likely to absorb water. When rainfall hits these landscapes, violent flash floods are more likely, along with mudslides and debris flows.

On July 16, heavy rainfall in western Colorado triggered flash flooding in Black Canyon of the Gunnison. At least three separate mudslides buried sections of East Portal Road - which is accessed from the park's South Rim - with up to 6 feet of debris, including areas that previously burned in the 2025 South Rim Fire. Rocks and mud also swallowed the park's East Portal campground and much of an adjoining picnic area, which will remain closed until further notice, along with the road. "There is currently no estimate of total damage, costs, or opening dates," a news release said.

More than 20 day-trippers, campers and anglers were trapped within the park because of the slides, and ground crews worked through the night using heavy equipment to clear the roads. All were able to exit the park by 9 a.m. the following morning, and no injuries were reported. 

A day later, however, on July 17, five members of a family were killed when a flash flood swept through a canyon just outside Capitol Reef National Park in southern Utah. Rainfall in the days before their visit had increased the likelihood of flash flooding. On the evening of July 17, other hikers discovered the body of one of the victims, and rescue personnel located the remaining victims by midday on June 18. The family included a fire captain from Provo, Utah, his wife, and the couple's three sons. Only their daughter, who was not on the trip, survived. 

The following day, Zion National Park closed its slot canyons to visitors over the risk of flash flooding. Among the closures was the park's Narrows hike - one of the most popular destinations in the park. Footage taken in the park last week documented massive, ephemeral waterfalls pouring off of the canyon walls and into the valley below.

Several regions are expecting heavy rain in the coming days, and the National Weather Service has noted that flash flooding remains "the foremost concern" across the Southwest. 

In a statement issued Monday by the agency's Grand Junction, Colorado, office - which includes Black Canyon of the Gunnison, Arches and Canyonlands National Park - the National Weather Service noted that strong storms could bring as much as 2 inches of rain per hour. "These rates could lead to flash flooding and debris flows especially over steep terrain and recent burn scars," the statement said, adding that "rain over the past several days has led to saturated soils, which increase the chances for excessive runoff."

Similarly, a flood watch has been issued until Wednesday for Capitol Reef National Park, Glen Canyon Recreation Area, parts of Canyonlands National Park and Zion National Park, including recent burn scars.

Visitors to these areas should monitor current conditions and abide by any closures. In particular, be sure to check the forecast far upstream of any potential hikes, as weather systems many miles away can cause flooding downstream. When hiking and camping, avoid low-lying areas or narrow slot canyons where escape may not be possible. Never drive through flood waters, even when they seem shallow. Lastly, always tell someone the details of your hike, including an expected end time. 

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