When Sandy and Craig McGill came up from their basement, instead of their roof, they saw a dark sky. "We had no clue it was going to be as bad as it was when we walked out and saw it," Craig said.

One such famous example among meteorologists is the May 28, 2013, EF3 tornado that hit near Bennington, Kansas. The twister traveled just 2.33 miles for an hour, and appeared to stop in place at ...