A Kelvin wave—a massive, slow-moving ocean phenomenon triggered by weakening trade winds during El Niño—is expected to reach California within days and could raise sea levels by up to a foot for months. Combined with this year's exceptionally strong El Niño, scientists warn of intensified storm surges, flooding, and coastal erosion threats throughout the winter. California has declared a state of emergency and is mobilizing resources to prepare for potential catastrophic impacts.