Humidity measures the water vapor present in the air, and Florida consistently ranks as one of the most humid states. To understand the state’s moisture, it is important to distinguish between two metrics. Relative humidity is the percentage of water vapor the air holds compared to its maximum capacity at that temperature. The dew point, by contrast, is the temperature at which the air becomes completely saturated. Because the dew point is a more direct indicator of the actual volume of moisture, it serves as a better measure of the familiar muggy feeling. Florida’s dew points frequently remain high, signaling the immense moisture load in its atmosphere.
Geographic Positioning Surrounded by Water
Florida’s unique geography as a low-lying peninsula is the primary reason for its perpetual atmospheric moisture. The state is nearly surrounded by massive, warm bodies of water: the Atlantic Ocean to the east and the Gulf of Mexico to the west. These warm waters provide an inexhaustible source for evaporation, continually supplying the atmosphere with water vapor. During the summer, the sea surface temperature along the Gulf Coast often exceeds 80°F (27°C).
This extensive envelope of warm water means the air above it is constantly taking on moisture. The warm Gulf Stream, a powerful ocean current, flows close to Florida’s Atlantic coastline, which also helps maintain high water temperatures year-round. Inland, the state’s vast network of shallow freshwater systems, including the massive Everglades—often called the “River of Grass”—further contributes to the local moisture supply. This huge, slow-moving sheet of water provides an immense surface area for continuous evaporation, perpetually recharging the humidity over the peninsula.
Prevailing Winds and Maritime Air
The constant supply of water vapor from the surrounding oceans is delivered inland by persistent wind patterns. Florida’s climate is overwhelmingly dominated by the Maritime Tropical (mT) air mass, which originates over the warm tropical waters of the Atlantic and the Gulf. This air mass is characterized by its high temperature and high moisture content. The movement of this air is primarily governed by the Bermuda High, a semi-permanent high-pressure system that anchors itself over the Atlantic during the warmer months.
The air circulates clockwise around this high-pressure center, effectively directing a steady stream of warm, moist air from the ocean directly across the state. This consistent flow prevents drier air masses, such as Continental Polar or Continental Tropical, from frequently reaching Florida. Consequently, the state rarely experiences the dry, crisp air that is common in continental interiors. The prevailing winds act as a constant atmospheric conveyor belt, ensuring that any moisture that precipitates out is swiftly replaced by new, saturated maritime air.
Temperature and the Capacity for Moisture
The final factor explaining Florida’s humidity is the direct relationship between air temperature and its capacity to hold water vapor. Warmer air molecules are more energetic and spread farther apart, allowing the air to physically hold a significantly greater volume of moisture before reaching saturation. The air’s capacity to hold water vapor roughly doubles with every 10°C (18°F) increase in temperature. Florida’s low latitude and intense solar radiation result in consistently high air temperatures, especially during the summer.
This high thermal energy gives the air a massive capacity for moisture, which the surrounding oceans and wind patterns continuously work to fill. The combination of a constant moisture source and air with a high capacity to hold it results in the consistently elevated dew points experienced throughout the state. Even if the relative humidity percentage drops during the hottest part of the day, the absolute amount of water vapor—the dew point—remains high because the maximum capacity of the warm air is so great.