HOUSTON- The first day of winter is shaped up to be a great day outdoors. People traveling by air and on the ground experienced dry weather and warm temperatures.

But the crowds inside Houston airports are slowly building into a holiday frenzy.

The Houston Airport System is anticipating more than 700,000 people to pass through Bush Intercontinental and Hobby Airport within the next three days.

Cristina Lopez and her family drove into Houston from Austin. They say a flight from IAH to Washington D.C. is more affordable out of the Space City.

“Visit my sister in D.C.,” said Lopez. “There is a total of 12 of us. We shipped all of our gifts to make it easier, that way we wouldn't have to worry while we're here.”

Travel experts say Thursday, Friday and Saturday will be the busiest days ahead of Christmas. The following Tuesday and Wednesday will be the busiest for travelers returning home.

“Plan for that,” said Bill Begley, spokesman for the Houston Airport System. "Know that you're going to see more people and you're going to have to give yourself a little extra time.”

Begley recommends people utilize www.fly2houston.com. The website offers real-time looks at parking availability, flight statuses, and TSA checkpoint wait times.

“It is a fantastic tool for travelers,” said Begley. “The more you know, the better it is.”