Some parents tell their children that thunderstorms occur when God goes bowling, but an observant youngster might wonder why The Big Guy only bowls in the summertime.

The short answer? "In the summer there's a lot more moisture in the air," says Yvette Richardson, assistant professor of meteorology at Penn State.

The wind crosses the plains like a steady gust from a blast furnace. The red terrain, flat and featureless, can't divert it. The few trees that inhabit the landscape lean permanently to the north. In the distance, giant Oklahoma and United States flags are pegged, rippling as they extend northward in a perfect line.