After a calm start to tornado season, the last two weeks of May unleashed a series of deadly tornadoes across the midwest.
The area hardest hit was central Oklahoma.
Tornadoes ripped through the area twice in two weeks, killing more than 3 dozen people.
The most recent severe storm struck Friday.
Among the dead - three veteran storm chasers:Tim Samaras, Paul Samaras, and Carl Young.
Officials say the tornado they were chasing was wrapped in rain and it took the scientists by surprise when it changed paths.
It was rush hour when Friday's violent storms struck and thousands of motorists were stuck on roadways with no place to take cover.
A mother and child were killed when their car was tossed from the road on the state's I-40 corridor.
Chief Meteorologist Chuck Collins says a car is the worst place to be during a tornado warning.
"Being mobile in a severe thunder storm or if a tornado is in the vicinity is the toughest position to be in, because your vehicle becomes a missile. It becomes a flying object. So you don't want to be in it. So you want to try and get out, get down low - if you can't get in a near by building that is structurally safe - just get down low into a ditch," Collins.
Collins advises motorists to not try and outrun the tornado and to avoid overpasses, as the winds can be sucked into the viaduct blowing you and anything else inside out.