South Dakota spins up the twister of the season.

Tim's team chases in the tornado twilight zone; Sean weathers controversy.

Storm and chasers collide in Minnesota for a final showdown.

The chase teams are on the front lines during an epic tornado outbreak.

The teams follow a storm headed toward downtown St. Louis.

Reed takes his team on a dangerous nighttime chase.

The teams help with the recovery effort in Alabama and Mississippi.

Reed and his team take the day off, but it backfires.

A tornado outbreak threatens to wreak havoc in Reed's backyard.

Sean tries his team's patience, and Tim makes questionable decisions.

The chase teams have one last chance to achieve their goals for the season.

The Twetos brave the elements to deliver supplies to inaccessible areas.

Jim arranges to transport the casket of the dark winter's first casualty.

The Tweto family takes full advantage of Alaska's summer conditions.

The pilots brave the elements as hurricane-force winds roar into Alaska.

A Greenhorn pilot goes on the most challenging run of his short career.