South Beach does not have four seasons. It has a dry half and a wet half, and then it has two weeks in the year that override both.
The dry half runs roughly from late November into April. Daytime highs sit in the mid-70s to low 80s Fahrenheit, the humidity drops to something northern visitors find pleasant, the rain mostly stops, and the sea is cool enough that some people find it bracing: sea surface temperatures bottom out around the mid-70s in February. This is also when a January cold front can push the island into the 50s overnight for two or three days, which surprises people who packed only swimwear. Hotel rates are at their highest across this whole stretch.
The wet half runs roughly May to October. Highs around 90, overnight lows that barely drop below 78, and sea temperatures reaching the mid-80s, which is bath-warm and lovely. The rain here is not the northern kind. Thunderstorms build inland over the Everglades through the morning, then drift east and reach the coast in the late afternoon, which means a bright hot morning, a violent half hour, and then a clear evening. Plan the beach for the morning and you will rarely lose a day. Rates are at their lowest, and the reasons are heat, storms and seaweed.
Then the two weeks that change the island. March is spring break, and on this island that is not a vague atmosphere but a set of published measures: restricted vehicle access on Ocean Drive on the peak weekends, a heavy police presence, and a crowd that is overwhelmingly young. Early December is Art Basel Miami Beach at the Convention Center, which fills every room on the island and roughly doubles what they cost.
There is also a seasonal fact that nobody advertises and everybody encounters: sargassum, the brown seaweed that arrives on the Atlantic beaches from roughly March through October and peaks in late spring and summer. The city clears the main stretch mechanically. It is not hidden, it is not anyone's fault, and 2026 has been a record year for it across the basin.
The rest of this page is the year, honestly, with the weeks worth booking and the weeks worth avoiding.