Miami's climate is classified as "tropical monsoon" which should tell you all you need to know about the weather! The climate is largely influenced by its proximity to the Tropic of Cancer and the Gulf Stream.
Summers are hot, humid, and long. Winters are warm, drier, and short. Spring and Fall are not well defined. January's temperature averages in the mid-60s and July averages in the mid-80s.
Triple digit temperatures are unheard of with Miami only breaking 100º once in the past 100 years.
Routinely, Miami is pounded by hurricanes between June 1st and November 30th, although the hurricanes don't necessarily pay attention to what date it is.