Urgent Flash Flood Warning: Impact Zones, Road Closures & Must-Know Safety Tips

The National Weather Service (NWS) has issued a series of flash flood warnings this weekend as late-season monsoon moisture collides with a stalled upper-level trough across the Southwestern United States. At midday Friday, warnings stretched from southern California’s desert counties through western Arizona and into parts of southern Nevada, with the most urgent alerts focused on Inyo County, CA, where thunderstorms have already dropped 1–2 inches of rain in less than an hour and flooded low-water crossings. Similar warnings remain in effect for Imperial County after overnight downpours sent washes surging and closed portions of Highway 78. Forecasters say deep tropical moisture will continue funneling north through Saturday evening, delivering rainfall rates that can overwhelm dry arroyo channels within minutes. Even areas that miss the heaviest storms remain vulnerable to sudden run-off as water races downstream from higher terrain. The NWS reminds residents that flash flooding can occur miles away from where rain is actually falling and often develops faster than new warnings can be issued. Key impacts expected through Sunday: • Rapid rises along normally dry washes, especially in the Owens Valley, the Mojave Desert, and western portions of the Sonoran Desert. • Mud and rock slides on mountain roads such as CA-190 through Death Valley National Park and AZ-89A in Oak Creek Canyon. • Brief but dangerous closures on interstates I-10, I-15, and I-40 where storm cells train over the same stretch of roadway. • Urban street flooding in Las Vegas, Phoenix, and Palm Springs during late-afternoon peak rainfall. Travelers are urged to monitor NOAA Weather Radio or weather.gov for updated flash flood warnings, avoid crossing flooded roadways—even if water appears shallow—and have multiple evacuation routes in mind. According to the NWS, just 12 inches of fast-moving water can sweep a small car off the road, while two feet can carry away most SUVs and pickup trucks. If you encounter a flooded intersection, turn around; do not attempt to drive through it. Preparedness tips: • Charge mobile devices before storms arrive and enable Wireless Emergency Alerts for real-time flash flood warnings. • Keep an emergency go-bag with drinking water, non-perishable food, flashlights, and basic first-aid supplies. • Secure outdoor furniture and construction materials that could be picked up by fast water and become hazardous debris. • Check on neighbors, particularly older adults and those living in low-lying manufactured-home communities. While showers may taper late Sunday, moisture pooling behind the trough could trigger additional slow-moving storms early next week. Residents across the Southwest should stay weather-aware and be ready to act quickly when the next flash flood warning is issued.