Travelers are bracing for another round of travel woes this Presidents' Day, as many parts of the country battle through snow and subzero temperatures.

On Monday, airlines cancelled thousands of flights as winter storm warnings were posted from Oklahoma to New Jersey and from Illinois to the Deep South as a band of snow and ice threatened almost 50 million people.

By Monday morning, Southwest had canceled over 150 flights  across the Midwest and Northeast, and an airline representative told FoxNews.com that they anticipate that number to rise through the day.

The airline is encouraging customers to check their flight status before heading to the airport. “Customers holding reservations through Tuesday, Feb. 17 have the option to proactively change their travel plans and can visit Southwest.com for more information.” 

An American Airlines spokeswoman confirmed that it has a travel policy in place covering 22 states in regions including the Northeast, Southwest and Midwest. Currently, people can change flights without a fee or get refunded on flights for travel up until Friday Feb. 20.

The airline said it is re-booking passengers as it cancels flights and moves planes out of affected areas to avoid future delays caused by snow removal and deicing. 

This adds to the more than 2,600 flights canceled on Sunday, including hundreds that were supposed to take off and land in Nashville and Memphis, Tennessee, and Charlotte, North Carolina, according to Flight Aware.com, the flight tracking website.

Forecasters predict a foot and a half of snow in pockets of Kentucky, Virginia and West Virginia before it swings into the Northeast on Monday night and Tuesday. Washington, D.C. was expecting as much as 8 inches of snow.

Meanwhile, Boston recorded another 13 inches of new snow Sunday and is bracing for yet another round of wintry weather. This is the sixth winter storm in three weeks, making February Boston’s snowiest month on record, with 58.5 inches. At 43.3 inches, the previous record was set in January 2005. The National Weather Service continues to forecast strong winds and bitterly cold temperatures in the Northeast.

The Associated Press contributed to this report.