Blaze burns out of control amid heat wave in Calif.

SAN MARCOS, Calif. -- Firefighters gained ground overnight on a string of major San Diego area wildfires - except for one in the city of San Marcos where the 700-acre blaze burned out of control Thursday as another scorcher day dawned.

Nine fires in all were burning an area of more than 14 square miles amid a heat wave and dry conditions, said San Diego County officials, who warned also of poor air quality with black and gray smoke wafting over the region. The wildfires drove tens of thousands from their homes and shut down schools and amusement parks, including Legoland.

Firefighters contended with temperatures approaching 100 degrees and gusty winds as they tried to contain flames fueled by brush and trees left brittle by drought.

Firefighter Martin Kennedy told CBS News correspondent Carter Evans that embers blown in high winds were firefighters' "No. 1 problem."

"Fire can travel basically the speed of the wind," said Kennedy. "So if you imagine if we're having 35, 45, 75 mile-an-hour wind, the fire can actually travel that fast."

Officials said a Carlsbad area blaze was 60 percent contained and had burned 400 acres. The wildfire destroyed an 18-unit condominium complex and four residences, Carlsbad Mayor Matt Hall said.

Some evacuation orders were being lifted in Carlsbad but a major power outage and hotspots were still a concern.

Efforts were focusing on San Marcos, a university city where hundreds of new evacuation orders were issued on Thursday. More than 20,000 evacuation notices were sent to residents Wednesday and a California State University campus with nearly 10,000 students in the middle of final exams was shut down at least through Thursday.

San Diego County officials said that the blaze had destroyed three homes.

Tuzo Jerger was one of thousands told to evacuate because of the Carlsbad fire. The 66-year-old real estate broker packed files, a surfboard, golf clubs, clothes and photos and sought solace at a friend's hilltop house in nearby San Marcos, only to see another fierce wildfire break out there and force thousands from their homes.

"I thought, 'Oh my God, it's going to come this way,'" Jerger said at a San Marcos restaurant where he found relief in a slice of pizza.

The blaze in the coastal city of Carlsbad, about 30 miles north of San Diego, was the most destructive of the fires so far.

Many schools across the county were closed Thursday including San Diego Unified. Officials expected some wouldn't reopen until next week.

Other areas in the county also flared up, though most calmed quickly, including two fires in the far north of the county near Camp Pendleton that together burned nearly 11 square miles and prompted evacuations that lasted just a few hours.

Gov. Jerry Brown declared a state of emergency for San Diego County, which would free up special resources and funding for the firefight, and state fire officials were creating a central command center for the blazes.

Drought conditions have made fire danger extremely high throughout much of California. Officials have encouraged residents in fire-prone areas to prepare evacuation plans and clear brush from near their homes.

The city's fire chief said the blazes were unprecedented in his 27-year firefighting career because they are so early in the year.

"This is May, this is unbelievable. This is something we should see in October," Chief Michael Davis said. "I haven't seen it this hot, this dry, this long in May."

Police and fire agencies were gathering evidence on the cause of the fires, but no conclusions had yet been reached.