Click to watch video

Windy conditions that whipped fires and ripped down power lines on Tuesday were expected again today, prompting the National Weather Service to issue a red flag warning beginning at 10 a.m.

The combination of strong winds – up to 35 mph – low relative humidity and dry vegetation will create what the weather service calls “critical fire weather conditions.”

The warning for North Texas counties remains in effect until 6 p.m.

A fire weather watch is in effect for Thursday, as westerly winds with gusts up to 45 mph are expected.

National Weather Service meteorologist Joe Harris advised that no "outside welding or burning should be performed today."

As of Tuesday, more than 150 counties were under a burn ban, according to the Texas Forest Service.

"Southerly winds will be increasing. Some areas may see 20 to 30 mph winds with higher gusts, especially northwest of the Metroplex. Winds will be slightly less southeast of the Metroplex," Mr. Harris said.

The windstorm that tore through North Texas on Tuesday drove fires that burned dozens of structures and hundreds of acres. It snapped trees, knocked out power to more than 75,000 people, left school administrators dithering about what to do with kids and had some drivers battling disabled traffic lights in evening rush hour. Power was restored by midnight to all customers, Oncor spokeswoman Carol Peters said.

The most serious damage was to nearly 30 structures, more than half of them homes, that burned to the ground in Paradise, in Wise County.

Authorities reported no serious injuries. One Benbrook firefighter was injured when the wind caught a truck door, slamming it against his hand. His hand, however, was not broken, said Benbrook fire chief Tommy Davis.

The winds were produced by two weather systems that stretched from Green Bay, Wis., to the Bahamas, forecasters said. By Tuesday night, those systems had drifted off to the east.

The risk of fires throughout the region will remain for at least the next two days, said Dan Shoemaker, a meteorologist with the National Weather Service.

Tuesday's wild weather started just about when many people take their mid-morning coffee break. According to the weather service, the wind speed at Dallas/Fort Worth International Airport was 15 mph just before 9 a.m. Two hours later, the speed reached 41 mph. The highest gust at the airport was 54 mph, just after noon.

Signs ripped from businesses. Roofs were pulled from buildings. Trees cracked in two.

GARY PAYNE / Denton Record-Chronicle

Denton firefighter David Hickman walked through thick brush to put out a grass fire on Tuesday.

At D/FW Airport, the winds caused 57 cancellations and delays of about 45 minutes, spokesman Brian Murnahan said. The airport handles 950 departures a day.

In Irving, the wind blew down a three-story concrete wall of an office building under construction in the 1900 block of John Carpenter Freeway. The wall fell on a forklift.

In Parker County, about a dozen buildings were damaged by fire. In Denton, Interstate 35 was among several roads closed briefly because of smoke.

Here's how the weather worked, according to Jason Dunn, another NWS meteorologist:

Far to the north, a huge low-pressure system spun. Late Tuesday afternoon, it was centered near Green Bay. Like its smaller tropical cousins – hurricanes and tropical storms – the unnamed system sent out waves of wind far from the center.

Meanwhile, a mound of high pressure sat over the Bahamas.

Where the two systems met, in a line that stretched from Green Bay to San Antonio, the collision set off the straight-line winds that knocked over signs, ripped down power lines and turned tiny brush fires into roaring blazes.

In Central Texas, a 500-acre fire in Burnet County was growing as it moved into Williamson County by evening. The area is not heavily populated, but some homes were evacuated and officials were concerned about livestock.

Six fires totaling about 150 acres south of Gainesville were either out or under control Tuesday afternoon, and no structures were damaged, officials said.

In West Texas, a fire near the small town of Maryneal in Nolan County destroyed about 200 acres. In Callahan County, a 300-acre fire jumped a road and continued spreading, destroying several buildings after about 80 families were evacuated.

Two volunteer firefighters were injured when an 18-wheeler driver whose vision was impaired by the smoke rear-ended their vehicle, officials said. One suffered a broken arm; the other had head and eye injuries.

Gov. Rick Perry has activated the state's Emergency Operations Center at level one, the highest level. Helicopters were on standby in Grand Prairie, Austin and San Antonio.

28 Structures that burned in the Wise County town of Paradise

59 Highest wind gusts, in mph, recorded in North Texas

57 Flight cancellations

at D/FW

2,400 Weight, in pounds, of containers blown over at a McKinney nursery

75,000 Residents who lost power

If you have been affected by the wildfires and need assistance, contact your local American Red Cross chapter. In Tarrant County, call 817-335-9137. In the Dallas area, call 214-678-4800.