Mazatlan is most comfortable from November to April, when daytime temperatures sit in the high 20s°C, humidity is low, and the rain holds off. This is also the busy season — flights and hotels fill, and Carnaval in late February or early March is the biggest party on the Mexican Pacific. Book months in advance for Carnaval week.
May and June are hot but dry; July to October is the rainy season — humid, with afternoon thunderstorms and an outside chance of a hurricane. Hotel rates are lowest then, and locals will tell you the city is at its greenest after the rains. Sport-fishing for marlin and sailfish peaks from May to October.