Leisure travelers heading into what is expected to be one of the busiest travel weekends of the year are already facing delays as severe storms move across the southern United States.

The severe storms in the region prompted the National Weather Service to issue multiple tornado warnings in two states through Thursday evening. Early Thursday, the Federal Aviation Administration ordered ground stops at two Texas airports, Dallas Fort Worth International Airport and Dallas Love Field Airport, and Texas Gov. Greg Abbott called for an emergency response as weather conditions worsened.

More than 700 flights within, to or from the United States were canceled Thursday, including hundreds of flights to or from Dallas-Fort Worth, according to flight tracking website Flight Aware.

In New Jersey, a gaping sinkhole opened along Interstate 80 in Wharton, in the eastern part of the state, prompting the state Department of Transportation to close the eastbound highway for emergency repairs.

In the South, more than a million people were under a tornado watch in parts of Louisiana and southeast Texas as of Thursday evening, according to the NWS.

A tornado warning was in effect for western and central Louisiana and extreme southeastern Texas until 2 a.m. Central Time, according to the Storm Prediction Center. This watch includes Lake Charles and Alexandria, Louisiana, as well as Port Arthur, Texas.

Severe thunderstorms will move from Texas to Louisiana Thursday evening, bringing a continued threat of tornadoes and strong winds.

“Thunderstorms will continue to pose a threat for some tornadoes this evening and into the early hours of the night as they spread east-northeast into portions of western and central Louisiana,” the Storm Prediction Center said. “Damaging wind speeds of up to 60-65 miles per hour and isolated hail may also occur,” it said.

According to the Storm Prediction Center, over 4 million people were under a level 3 out of 5 severe storm threat in southeast Texas, including Houston, as of Thursday afternoon. The center is warning of multiple tornadoes, including one or two strong tornadoes, and large hail from East Texas this afternoon and overnight to Louisiana, southern Arkansas and well west of central Mississippi.

Gov. Abbott directed the Texas Department of Emergency Management on Thursday to activate state emergency resources ahead of the severe weather threat in the eastern part of the state, he announced on X.

“As Texans and out-of-state visitors begin traveling after the Christmas holiday, it is critical that everyone regularly monitor road conditions, prepare an emergency plan and follow guidance from state and local officials,” Abbott said in a news release.

The threat of a severe storm is expected to increase across the Southern Plains and Lower Mississippi River Valley through Thursday afternoon and is expected to continue into the evening as a low pressure system strengthens across the region.

Storms could potentially bring severe wind gusts, damaging hail and some tornadoes to cities like Houston and Austin.

An isolated severe storm threat is spreading across central Texas into central Arkansas, western Mississippi and southern Louisiana, including cities such as Dallas, Fort Worth, Little Rock and Baton Rouge. The total population exposed to a severe storm threat on Thursday exceeds 20 million people.

There is a strong risk of storms this weekend

The severe storm threat is expected to decrease across the South on Friday but increase again on Saturday.

“It appears that all severe weather modes and hazards could occur, including large hail, damaging winds and tornadoes, as storms develop steadily east-northeast Saturday afternoon and Saturday evening,” the Storm Prediction Center warns.

Cities like Houston, Memphis, New Orleans, Birmingham and Montgomery could have a lower chance of storms on Saturday.

This series of storms could impact the East Coast through Sunday, potentially causing additional delays for those traveling home from the holidays.

According to AAA, record numbers of travelers are expected by 2024. The association expects that from December 21 to January 1, 119.3 million people will travel 50 miles or more from home. That is 3 million more travelers than in the same period last year.

Atmospheric river storms rage on the West Coast

Meanwhile, on the West Coast, a very active weather pattern is bringing coastal rains, gusty winds, snowfall in the mountains and dangerous waves to the region as travelers head home for the holidays.

High wind warnings are in effect for the lower elevations of the Northwest and Northern California, where winds of 40 to 60 mph and isolated gusts of more than 65 mph are expected.

“Damaging winds will knock down trees and power lines. Large-scale power outages are expected. Travel will be difficult, especially for high-profile vehicles,” the National Weather Service warned.

The winds are increasing high waves across most of the West Coast, where a number of warnings are in effect for high surf and coastal flooding.

Winter weather advisories are in effect for portions of the Cascades, Sierra Nevada and Rocky Mountains as bouts of moisture continue to hit the West. Snowfall of 6 to 18+ inches and gusts potentially exceeding 70 mph could reduce visibility, make travel nearly impossible, and cause damage to trees and power lines.

The next in a series of atmospheric river-borne storms is expected to bring another round of coastal and valley precipitation, mountain snowfall, gusty winds and high surf to the West on Friday, while more storms are likely to impact the region on Saturday and Sunday become.

CNN’s Sharif Paget contributed to this report.

For more CNN news and newsletters, create an account at CNN.com