A large storm front is moving across the Midwest on Sunday afternoon, with Oklahoma under a level 4 out of 5 “moderate risk” for severe storms.

“The greatest threat for severe weather will be over parts of Oklahoma and north Texas this afternoon and evening. Tornadoes (some capable of significant/EF2+ damage), destructive hail, and severe gusts all are possible,” Storm Prediction Center reported.

The severe weather is due to a cold front mixing in with warm and muggy air from the Southern Plains which creates a perfect combination for severe storms.

The highest threat of tornados will in parts of Oklahoma and north Texas. Millions of residents are expected to be impacted.

The Dallas-Fort Worth metro area and Fort Smith, Arkansas, are under a level 3 “enhanced” risk while Springfield, Missouri, as well as the Texas cities of Waco and Wichita Falls are under a level 2 "slight" risk. Roughly 20 million people at risk from the storm front.

"Interstate 35 from Dallas to Oklahoma City will be especially busy Sunday due to the 'Red River Rivalry game' between Texas and Oklahoma that took place on Saturday," CNN meteorologist Allison Chinchar said.

"This means a lot of fans could be driving back home this afternoon and evening -- peak timing for the storms."