Has there ever been a day when there was no precipitation anywhere in the United States?
—Lisa Fionda, St. John, Ind.
It’s highly unlikely. On rare occasions, there may be a few precipitation-free hours across the Lower 48, but certainly not through an entire 24-hour period. Because of the nation’s great size, at least one or two precipitation-generating weather systems almost always are present. But even lacking organized storm systems, isolated afternoon thunderstorms are a certainty across the mountainous terrain of the West during the warm season, and lake-effect snow is usually present somewhere in the Great Lakes region during the cold season. Finally, moist air pushing inland from the Pacific usually generates at least a few patches of rain or snow as it confronts the higher eleva- tions of coastal mountains.