Severe thunderstorms and tornadoes affect communities across the U.S. every year, causing fatalities, destroying property and crops, and disrupting businesses. Tornadoes are the most destructive products of severe thunderstorms. Damages from violent tornadoes seem to be increasing, similar to the trend for other natural hazards in part due to changing population, demographics, and more weather-sensitive infrastructure and some analysts indicate that losses of $1 billion or more from single tornado events are becoming more frequent. Insurance industry analysts state that tornadoes, severe thunderstorms, and related weather events have caused nearly 57%, on average, of all insured catastrophe losses in the U.S. in any given year since 1953. Contents of this report: (1) Overview; (2) Issues for Congress: A Focus on Local Warnings and Forecasts for the National Weather Service; Mitigation: The National Windstorm Impact Reduction Program; Reauthorizing the National Windstorm Impact Reduction Program; Climate Change and Severe Weather: The April and May 2011 Tornados: A Link to Climate Change?; Other Factors Contributing to Risk From Tornadoes; Forecasting and Warning: The Role of the National Weather Service; Summary and Conclusions; Appendix: Risk from Severe Thunderstorms and Tornadoes. Map and tables. This is a print on demand report.