The foggy season for Florida is typically during the winter months. Although we do get fog in the Summer, it's the widespread advection (sea) fog that is more prevalent during the cold season.
On average, the Suncoast will see about 15 episodes of dense fog. When the visibilities drop below 1/4 of a mile that's when it can get very dangerous to drive. The National Weather Service will issue a dense fog advisory when visibilities are anticipated to be less than 1/4 mile for at least 2 hours.
This past weekend the fog was so thick, that the Sunshine Skyway bridge was closed for a short period of time. This was due to the sea fog rolling in. This happens during the winter typically, as the warm moist air out of the south moves over the relatively cool waters of the Gulf of Mexico. This is the really thick kind of fog that covers a large area.
Some of the worst accidents in the State can be attributed to foggy conditions. January 30th 2012, 10 people died on I-75 near Gainsville due to a deadly combination of fog and smoke. Smoke can increase the intensity of the fog. If the visibility becomes so bad, pull far enough off the road and turn your emergency flashers on.
In January 2008, five people were killed, in a 70-vehicle pileup on Interstate 4 in Polk County. That string of wrecks also injured 38 people and occurred in heavy fog and smoke.
More people have been killed as a result of fog than hurricanes here in Florida over the past 10 years. When a dense fog advisory is issued it's best to postpone any unnecessary travel for the time of the advisory. And even though it may not be foggy in your neighborhood, it possible, that it might be thick as pea soup right around the corner.
If you do have to drive in the fog, remember to use your low beams. Using your high powered beams only causes more problems as the light is reflected back to you, thus limiting your ability to see.