It's tornado season for much of the country, with April, May and June being the most active months for tornadoes,  according to the National Oceanic and Atmospheric Administration's National Climatic Data Center.

Tornadoes frequently occur in other countries, such as Australia and New Zealand, and across Europe and Asia, but the United States has more tornadoes for its size than any other country.

The costliest U.S. tornado outbreaks in terms of insured losses were in the billions of dollars, with the top three occurring in just the past five years. According to the Insurance Information Institute and Property Claims Services, the tornadoes that hit Tuscaloosa and Hackenberg, Ala., April 22-28, 2011, caused $7.6 billion in insured losses and affected 13 states.