As you click through the maps, you will see that the risk of tornadoes is mainly confined to the South during the first two months of the year. The South then typically sees its greatest threat of tornadoes as we head into the months of March and April.
From April through June, the biggest tornado threat shifts to the Plains, Upper Midwest and Great Lakes as the jet stream retreats northward with time. The main tornado risk then stays along the northern tier of the country through much of the summer, however tropical storms and hurricanes can increase the threat in the South as they move inland.
As we head into the months of November and December, the greatest chance of tornadoes moves back to the South.