Beach hazard warnings are in effect Monday for Illinois, Indiana, Michigan and Wisconsin, and along nearly the entire California coastline, with forecasters warning of waves up to 10 feet and dangerous rip currents through midweek.
The four Great Lakes states all sit along Lake Michigan, and officials say major cities including Chicago and Milwaukee will face disruption this week. Waves of up to nine feet are expected to last until at least Tuesday night, with high waves capable of swamping piers and sweeping people into the water. Two dozen beaches in Chicago have already banned swimming unless a lifeguard is on duty.
The dangerous conditions have been blamed on a cold front passing through the region, combining with persistent north winds blowing down Lake Michigan that are pushing up waves and strengthening currents along the shore.
California coast under similar threat
In California, nearly the entire coastline from San Diego to San Francisco is under a warning from the National Weather Service, with waves up to 10 feet, dangerous rip currents and coastal flooding in some areas expected to make beaches hazardous until Wednesday night.
Forecasters say a long-period swell, made up of waves that have traveled long distances across the Pacific from the south and southwest, is behind the disturbance. These waves are larger and more powerful than normal, producing bigger breaking waves, sudden "sneaker" waves that can rush far up the beach without warning, and strong currents that can pull people into deeper water.
Officials say sneaker waves in California this week will be powerful enough to move large objects in the water. A spokesman for the NWS warned: "Large, unexpected waves can sweep across the beach without warning, sweeping people into the sea from rocks, jetties, and beaches." The spokesman added: "These sneaker waves can also move large objects such as logs, crushing anyone caught underneath."
Officials have urged beachgoers in every affected state to never turn their backs on the ocean, and warned that calm-looking surface conditions can be misleading, since sneaker waves in California can strike after quieter periods.
A spokesman for the Chicago Park District said: "Only swim at beaches when lifeguards are on duty from 11am to 7pm daily. Swimming anywhere else along the lakefront is strictly prohibited and dangerous."
A rip current is a strong, narrow channel of water that flows quickly away from the shore, often pulling swimmers out to sea. They can be deadly even for strong swimmers, sweeping people into deeper water and exhausting them if they fight the current instead of swimming parallel to the shore.
Beach hazard warnings cover multiple Wisconsin counties, including Sheboygan, Ozaukee, Milwaukee, Racine and Kenosha, home to approximately 1.5 million people. In Illinois, Lake County and Northern and Central Cook counties are under the same warning; roughly two million people visit Chicago-area beaches each year.
In Indiana, Lake, Porter and Northern La Porte counties are affected, while in Michigan the warning covers Mason, Oceana, Muskegon, Ottawa, Allegan, Van Buren, Northern and Southern Berrien, and Manistee counties. Officials say beach conditions may be dangerous through Monday and Tuesday.
NWS officials in Los Angeles said: "There is an increased risk of ocean drowning. Rip currents can pull swimmers and surfers out to sea. Waves can wash people off beaches and rocks, and capsize small boats nearshore." They advised anyone heading to the California coast this week to avoid venturing onto local piers and to stay within eyesight of lifeguard towers if they choose to swim.
