How often do F4/F5 tornadoes occur?
Of the 1000 tornadoes that occur each year, about 2% of them are rated F4 or F5. That means that there are as many as 20 devastating tornadoes each year. It is possible that meteorologists have underestimated the number of violent tornadoes that occur each year. Tornadoes are rated only by damage they do to man-made structures. Therefore, if a tornado doesn’t hit a structure of some kind, we cannot estimate its strength. Also, a tornado varies in strength during its lifetime and could be its strongest while between areas of houses or other buildings.
