One, peninsulas are naturally warmer than mainlands because the adjacent water absorbs the sun's warmth and heats up the land it surrounds. And two, Florida's land is 75% coastal and as air moves across the warm water it picks up heat and water vapors, making Florida the most humid in the country.

The reason Miami feels much hotter than its actual temperature suggests is a combination of high relative humidity and the Urban Heat Island effect. Because Miami is a coastal city surrounded by the Everglades and the Atlantic Ocean, the air is constantly saturated with moisture. When humidity is high, your sweat cannot evaporate from your skin as quickly, which is the body's primary way of cooling down. This causes the "Heat Index" (the "Feels Like" temperature) to be significantly higher than the number on the thermometer; a 90°F day with 80% humidity can easily feel like 105°F. Furthermore, Miami's dense landscape of concrete, asphalt, and glass buildings absorbs solar radiation during the day and re-emits it at night, preventing the city from cooling down effectively. In 2026, the effects of climate change have also led to more "stagnant" air patterns and warmer ocean temperatures, which further trap heat over the city. This creates a "heavy," oppressive feeling to the air that is a signature of the South Florida climate, especially between the months of June and September.