"This is our 'normal' fire season," said John Saddler, a fire manager for the Florida Division of Forestry.

Saddler said conditions were so dry that it would take a significant amount of rain to make a difference.

At least four people have been killed in smoke- and fog-related highway crashes -- two in a five-car pile-up on Interstate 95 in Brevard County on Sunday and two in accidents in Palm Beach County on Monday, the Florida Highway Patrol said.

Bush declared a state of emergency Monday night and put the National Guard on stand-by alert. National Guard crews prepared three helicopters with giant water buckets to join the fight against the fires.

"We haven't been called up. We have been given the be-prepared signal," said Jon Myatt, spokesman for the Florida Department of Military Affairs, which runs the Florida National Guard for deployments on wildfires and other emergencies.

On Florida's east central coast, a 6,000-acre (2,400-hectare) fire has burned for nearly two weeks in Brevard County, some 60 miles (95 km) north of the Kennedy Space Center. That one destroyed a home in New Smyrna Beach.

Farther north in Volusia County, 1,000 homes were evacuated near a 1,400-acre (560-hectare) fire.

Billowing smoke from those two fires forced periodic shutdowns of Interstate 95, a major north-south artery. The highway was reopened on Tuesday but the troopers were keeping close watch.

"There's still smoke up in that area," Florida Highway Patrol spokeswoman Kim Miller said. "The median was on fire, that was the problem there."

On the west side of the state near Tampa, smoke from a 450-acre (180-hectare) fire ignited by a power line forced the shutdown of Interstate 75 for part of Monday. (Additional reporting by Jim Loney)