Florida is known as the Sunshine State with good reason. The sun shines three fourths of the possible sunlight hours annually, ranging from 70 percent in December to 84 percent in April. The Keys, being the farthest point south experiences the most intense solar radiation in the state.

Solar radiation in the Keys varies with factors which modify the transmission, absorption, and reflection of solar energy. These include factors such as cloud cover, air pollution (particulate load or dustiness), and relative humidity. These factors result in temporal and spatial variations in the amount of solar radiation reaching the land and water surfaces.