Whenever the cool sea breeze collides with the hot & humid inland air. The day usually starts out cloudless and then small clouds begin to appear. Anytime after 2:00 pm thunderheads begin to appear and then build over the rest of the afternoon. They often become massive and encompase the entire Central Florida reigion lingering into the evening hours. Other times they are scattered and last just a few minutes when they hit cooling the tempreture and usually gone for the rest of the day.