Since allergist William "Bill" Hark's home state of offers few storm-chasing opportunities, he spends summer vacations in – you guessed it – Tornado Alley. Stretching from central to and , Tornado Alley is where tornadoes occur most frequently. Twisters are spawned from the massive rotating thunderstorms (supercells) created when warm, humid air from the Gulf of Mexico meets the drier air coming from the north and west.

Despite close calls, Hark says he has never felt that he was in any real danger while chasing storms. Continuous storm data is readily available on the internet, along with computer models, satellite, and radar images. Hark and fellow chasers pool their information, interpret the data, and use forecasting skills honed from years of chasing.

Armed only with cameras, Hark gets up closer than most people to terrifying weather extremes. The payback? Footage of ominous supercells, tornadoes, and unusual cloud formations, some of which he sells to TV stations. For all their destructive power, severe storms can produce images of remarkable beauty. Declares Hark, "Facing what Mother Nature can dish out is a rush."

Many of these photos can be seen on his website.