An enormous, hazy cloud of dust from the Sahara Desert is blowing toward the southern United States, but meteorologists do not expect much effect beyond colorful sunsets. The leading edge of the cloud -- nearly the size of the continental United States -- should move across Florida sometime from Monday through Wednesday. "This is not going to be a tremendous event, but it will be kind of interesting," said Jim Lushine, a severe weather expert with the National Weather Service in Miami. He said the dust could make sunrises and sunsets spectacular. It might not have much effect on the rest of the country, said Scott Kelly, a meteorologist with the weather service in Melbourne. "Maybe south Texas or Mexico if that dust cloud keeps moving westward, but nothing north of Florida, unless a weather system can dive southward and pull that air northward," he said. Such dust clouds are not uncommon, especially at this time of year. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward. If the dust is concentrated enough, it could create some problems for people with respiratory problems, said Ken Larson, a natural resource specialist with the Broward County Environmental Protection Department. "If somebody is subject to a respiratory condition, if they see hazy skies, they might want to take a little more precaution, not participate in strenuous activity and stay indoors," Larson said.