Help Tornado tips Tornado danger signs An approaching cloud of debris can mark the location of a tornado even if a funnel is not visible. Before a tornado hits, the wind may die down and the air may become still.
Tornadoes generally occur near the trailing edge of a thunderstorm.
It is not uncommon to see clear, sunlit skies behind a tornado. The state reported a record number of tornadoes in 1998, but nearly two-thirds of them were the weakest kind, according to the National Weather Service. The Weather Service said there were 78 tornadoes in Iowa in 1998. That surpasses the previous record of 71 in 1990. The strongest tornadoes measured are F-5s.