Here's an article form Orlando Sentinel on dust storm:

As if this hurricane season weren't tumultuous enough, Central Florida -- and the rest of the Southeast -- is about to get hit by a sandstorm.

By Monday or Tuesday, a Sahara dust outbreak, or a cloud of what originally was African sand carried across the Atlantic on the back of a tropical wave, is expected to settle over the region for about 12 hours, forecasters said.

It might turn the skies milkier and leave a light coating of reddish-brown dust on your car, the result of a small amount of iron content. It also could make the sunrise and sunset spectacular, said Jim Lushine of the National Weather Service in Miami.

"It's just kind of an interesting phenomenon," he said. "You might see it better in the morning, when the angle of the sun is low."

Usually, such dust clouds are too diluted to cause health problems or reduce visibility for aircraft pilots.

On the other hand, if concentrated enough, the outbreak could raise the air-quality index into the unhealthy range for people with respiratory problems, said Ken Larson, a natural-resource specialist in South Florida.

Dust outbreaks, which are most common in early July, start when tropical waves lift sand from the Sahara to about 10,000 feet, where it is reduced to even smaller particles. The dust then drifts west on a dry tropical wave, as opposed to a moist tropical wave, which can spin into a hurricane.

The dust cloud aiming this way is huge, about 2,500 miles from west to east and 1,500 miles from north to south, or almost as big as the United States, Lushine said.

By today, the outbreak should be about 1,400 miles east of Miami, moving west at 345 miles per day, about the same pace as a tropical system.

Because the Sahara dust carries some pathogens, it might harm coral reefs, particularly in the Caribbean, said Bernhard Riegl, an associate professor at Nova Southeastern University's Oceanographic Center.

"Entire desert locusts, the insects, have made it across the Atlantic to the Windward Islands," Riegl said.

One good side effect: "It's difficult for tropical-storm development to occur in these dust outbreaks," Lushine said.