High winds are one of the nation's leading damage- producing storm conditions. They do not come from winter storms, tornadoes, nor hurricanes, but are strong winds generated by deep low pressure centers, thunderstorms, squall lines, or by flow over mountain ranges. The annual average property and crop losses from windstorms total $379 million, and windstorms over the past 46 years have caused between 6 and 35 deaths each year. Windstorms range in size from a few hundred to a hundred thousand square miles, being largest in the western U.S. where 40 percent of all storms exceed 50,000 square miles. Ten percent of high wind events in summer are 10,000 square miles or larger, whereas 10 percent of winter storms are over 100,000 square miles. In the eastern two-thirds of the nation, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western U.S., point averages are 1.9 storms per year. Midwestern states average between 15 and 20 windstorms annually; states in the East average between 10 and 25 storms per year; and West Coast states experience 26 to 30 storms annually.
Storms causing insured property losses >$1 million, labeled catastrophes, were assessed, and 176 such windstorms occurred during 1952- 2006, an average of 3.2 nationally. Catastrophic windstorms were most frequent in the Central, Northeast, West, and Northwest climate regions, and least often in the High Plains. More than half of the catastrophes (56 percent) occurred in only one state. Catastrophic storm losses were highest in the West and Northwest regions, the only form of severe weather in the U.S. to maximize losses on the West Coast. Most western storms occurred in the winter as a result of Pacific lows, and California has had 31 catastrophes, more damaging windstorms than any other state. The national temporal distribution of the catastrophic windstorms during 1952-2006 has a flat trend, but their losses display a distinct upward trend with time, peaking during 1996-2006.