MEXICO CITY—Hurricane Otis made landfall on Mexico’s Pacific Coast as a powerful Category 5 storm, as authorities warned of torrential rain, landslides and flash flooding.

Authorities urged people living near rivers or ravines to evacuate. Mexican President Andrés Manuel López Obrador late Tuesday said he instructed the country’s army and navy to assist state and city authorities in providing aid and shelter, clearing roads and highways and distributing food and water.