DALLAS - Gov. Rick Perry activated 250 Texas National Guard troops Saturday night and authorized the use of 75 Humvees to help transportation officials and local authorities along the projected path of expected ice storms.

Perry spokesman Robert Black said the move was a precautionary measure.

"Local communities are doing a good job of deploying assets and preparing for the worst," Black said. "The governor wants to make sure adequate backup is where it is needed."

A large storm that brought a mix of heavy rain and strong winds across a large swath of Texas on Saturday is expected to turn roadways to ice as temperatures drop below freezing on Sunday.

A meteorologist with the National Weather Service said overnight freezing rain could bring icy conditions across Dallas-Fort Worth.

"It looks like more freezing rain on Sunday and that is the main area of concern because at that point we'll have subfreezing temperatures as well as some moderate or heavy precipitation," meteorologist Jesse Moore said. "That's what we expect to cause some of the problems."

At least 13 homes, several businesses and the San Marcos Police Department's headquarters were damaged Saturday by a large storm that was later determined to be a tornado, San Marcos spokeswoman Stephanie Garcia said.

The storm blew out windows and collapsed a wall at the police department building, and ripped the roofs off of nearby homes and businesses, said Melissa Millecam, communications manager for the city.

It also caused minor damage to the Texas High School Football Coaches Association building, Garcia said. No injuries in the city some 30 miles south of Austin were reported, however.

The same storm on Saturday morning toppled power lines along Interstate 35, closing the busy north-south highway for three hours while crews removed the fallen lines, Millecam added.

"It's a good bit of damage," she said. "It's still stormy and we've got power outages in different places."

Across Central Texas, meanwhile, there were widespread reports of high water rescues and flooding after more than 6 inches of rain fell in some spots.

Lt. Matt Cox of the Austin Fire Department said firefighters pulled a homeless man from the section of Waller Creek that runs through downtown Saturday morning. Although the man was not seriously injured, he told rescuers he had gone into the water to try to help a woman he had seen struggling there.

Cox said the department launched boats and deployed searchers along the creek down to its confluence with the Colorado River, but they saw no sign of the woman.

Cox said he believes the woman may have been able to escape the creek. He said the department had helped close down dozens of roads throughout town and was assisting in many minor rescues.

An ice storm warning was in effect until Monday morning for much of North Texas, including Dallas and Fort Worth, where residents braced for a slick mixture of sleet, freezing rain and snow.

About 300 flights were canceled Saturday at Dallas-Fort Worth International Airport, spokesman David Magana said. He said crews had begun deicing airplanes before takeoff, creating further delays.

Deicing will continue Sunday, airport spokesman Ken Capps said. Airport concessionaires stayed open throughout the night to assist passengers still in the terminals.

"We are ready to sand roadways and runways as needed as temperatures drop," Capps said.

TXU Electric Delivery, which serves power to more than 3 million homes and businesses, reported outages to about 12,000 customers Saturday. Most of them were in Fort Worth. About 1,100 customers remained without power Saturday evening, spokeswoman Carol Peters said.

The storm forced the cancellation of several events Saturday, including a Dallas parade and banquet that was part of the city's Martin Luther King Jr. festivities. The Fort Worth Stock Show and Rodeo parade was also called off.

The University of Texas at Austin canceled its Martin Luther King Day march scheduled for Monday morning, school spokesman Robert Meckel said.