Hiking canyons can quickly turn deadly when storms hit – what you should know before going in

Canyons are narrow, steep valleys that act like channels for water during heavy rainfall. Even if rain falls far upstream or outside the canyon, the water can rush into the canyon quickly due to the steep terrain. For example, in the Grand Canyon on August 29, 2026, monsoon storms sent a sudden flood into a narrow part of the canyon, trapping hikers. These floods are called flash floods because they happen rapidly and with little warning. The Grand Canyon flood involved heavy downpours typical of monsoon season, which lasts from mid-June to September in Arizona. In arid regions like Arizona or Israel’s Negev Desert, dry ground forms hardened crusts that prevent water from soaking into the soil, making flooding worse. In 2018, a flash flood in Israel’s Tzafit Canyon killed 10 hikers, showing how quickly water can rise in such environments. A year’s worth of rain fell in a single day during that event.

The ability of the ground to absorb water, called porosity and permeability, affects flood risks. Porous and permeable soils allow water to sink into the ground, reducing surface flooding. However, in dry areas like Arizona or the Negev Desert, the soil often hardens into a crust, making it harder for water to penetrate. This forces water to flow over the surface instead, increasing the speed and volume of floods. Vegetation also plays a role: areas with little plant cover, common in deserts, allow water to flow more rapidly down slopes. For instance, the hardened crusts and lack of vegetation in these regions contributed to the deadly floods in the Grand Canyon in 2026 and Tzafit Canyon in 2018. Understanding these conditions helps explain why floods in canyons can be so sudden and destructive.

Two recent incidents highlight the deadly potential of canyon floods. In the Grand Canyon on August 29, 2026, a flash flood killed at least two hikers and left a third missing. Survivors described water rising rapidly over the trail, forcing them to cling to ledges while fearing for their lives. In 2018, a flash flood in Israel’s Tzafit Canyon claimed the lives of 10 high school graduates. Both events occurred in arid regions during monsoon season, where heavy rainfall overwhelmed the hardened ground. The floods stranded people for hours, with some trapped for over 48 hours. These examples demonstrate how quickly conditions can change in canyons, even under clear skies, and why hikers must remain vigilant.

Hikers can recognize an impending flood by paying attention to specific warning signs. Muddy water or debris in a normally clear stream often indicates that a flood is developing upstream. The sound of rushing water, sometimes described as resembling a freight train, is another clear alert. Weather conditions also provide clues: heavy rain upstream, even if the sky above the canyon is clear, can lead to a sudden flood. The National Weather Service issues warnings for flash floods, but cellular service is often unreliable in deep canyons. For example, in the Grand Canyon flood, survivors reported hearing the roar of the water before it arrived. Rising water levels or the distant sound of rushing water should prompt immediate action to seek higher ground.

Proper preparation is essential for safe canyon hiking. Start by studying the terrain and escape routes to ensure you can reach safety quickly if a flood occurs. Talk to park rangers to learn about current conditions and share your hiking plans with someone responsible. Always check the weather forecast not only for your location but also for areas upstream, as rain far away can still cause flooding. Carry essential gear such as a flashlight with extra batteries, a whistle to signal for help, and extra clothes in case you get wet. In high-risk areas, consider using an inflatable personal flotation device. For example, the National Weather Service provides flash flood warnings, but hikers must rely on their own awareness and preparation to stay safe.