Helene strengthened into a Category 4 hurricane hours ahead of its expected landfall on Florida’s northwest coast Thursday night, and forecasters warned that the enormous storm could create a “nightmare” surge in coastal areas and bring dangerous winds and rain across much of the southeastern U.

Tropical Storm Helene is rapidly strengthening in the Caribbean Sea and is expected to become a hurricane while moving north along Mexico’s coast toward the U.S. The storm has prompted residents to evacuate,