The climate regime of the municipality of Mazatlán is transitional Tropical wet and dry (Köppen climate classification Aw), with a marked dry season in the winter; however, as it is at the transition zone with the semi-arid climate to the north (BSh), the dry season is longer and more arid than most areas of similar classification. The wet season (July to September) is short, very rainy, and very humid.
During the 1940-1980 period, the municipality saw an average annual rainfall of 748 mm, a maximum of 215.4 mm in 24 hours, and 90.4 millimeters in one hour. During this same period, the average rate of evaporation was 2146.80 mm. The prevailing winds are from the northwest at an average speed of 5.0 meters per second (18 km/h).
In January 2008, the lowest recorded temperature in Mazatlán thus far during this century occurred at 2°C, despite the city's location in the Tropic of Cancer
