Flash flooding tore through the Grand Canyon, bringing conditions that rapidly deteriorated in just a few minutes. Several factors can lead to these life-threatening conditions for hikers, even when sunshine is present overhead.

A slot canyon is a long, narrow channel that is much deeper than it is wide and is extremely prone to flooding. These canyons are especially scary because they are difficult to impossible to get to higher ground while hiking in them.

While the Grand Canyon is not technically a slot canyon, it contains canyons that can behave very similarly to slot canyons and can bring rushing waters and life-threatening conditions for hikers.

Here are a few reasons that these slot canyons can be so dangerous:

Sunshine overhead does not mean safety. A rainstorm upstream can drop heavy rainfall while the sun shines overhead for you. But that water will come downstream to your location. And if you are in a narrower canyon, water rushing downstream to you is being funneled into your narrower canyon. When that happens, water has nowhere to go but up.

Water levels can jump feet in seconds, which means that if you have no higher ground to reach, you could get hit by water moving at the speed of a vehicle on the road, even if the sun is out.

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If you decide to hike in narrower canyons, it is essential that you check the weather the day of your hike. But it isn't just about checking the weather at your current location. You have to check your surrounding areas as well, specifically upstream from your location.

Harder ground near the canyons cannot absorb the rain. The soil in the Desert Southwest doesn't work like loamy soil in other parts of the country. When it rains in these areas, it will just run off. And many of these canyons see very little rainfall all year round. So, it doesn't take much to see several months' worth of rain.

It isn't just water. As sand, rocks, and other debris collect in the water, the power of the material multiplies. These debris flows are extremely dangerous, fast-moving mixtures that can quickly overwhelm those in these lower elevations.

Burn scars make it worse. Rain also fell on part of the Dragon Bravo burn scar, a burn area left by a lightning-caused wildfire in July 2025 that torched more than 227 square miles (590 square kilometers).

Burn scars occur when wildfires burn the top layer of soil, turning it into an ashy material that almost resembles pavement. This layer is very water repellent and can lead to even more flash flooding in canyon areas.

Service can be spotty in these canyon areas. That means warnings from our app or the National Weather Service could be hard to receive, but the option of renting a satellite phone is a possibility and could very well save your life should conditions suddenly take a turn for the worse.

Labor Day plans?

If you were planning on hiking some of these canyons for the Labor Day Weekend, these plans may have to be canceled or changed.

Regardless on where you go hiking, let loved ones know where you are going to hike before you move into a place with potentially no service. Also, if storms are in your area, avoid narrow canyons and only hike in places where some sort of higher ground is available.

Also pack essential items like sun protection, insulation, extra layers, a flashlight, first aid, snacks, extra water and even items like a helmet, a life jacket and bug repellent.

It doesn't hurt to add a whistle for every person in the group, especially children. Three blasts is the distress signal, and it carries far further than a voice.

Should you hike, set a turnaround time before you start, so you aren't caught out later than you would prefer. Also, identify escape routes in advance. It is ideal that these escapes allow you to get to higher ground.

Also, know your limits when hiking. Don't overdo it.

There are many locations that are closed until further notice, including: Phantom Ranch, including its canteen and cabins; Bright Angel Campground; the entire North Kaibab Trail from the trailhead to Phantom Ranch; and both the Black Bridge and Silver Bridge over the Colorado River.

Hiking during the monsoon season is a very risky endeavor. Pop-up storms can quickly drop heavy and very localized rainfall. If you see rainfall in the forecast anywhere near your location, hiking in canyons is not advised.