Weather: Partly to Mostly Cloudy

Partly to Mostly Cloudy

One of the great wonders of the universe is that our planet is surrounded by a unique blend of compounds, including water in its vaporous state. Actually, water is pretty big on the surface of our planet itself. More than 75 percent of the earth's surface consists of water. Maybe this should be called planet Ocean rather than planet Earth. There really is water everywhere, and the big forecasting challenge each day is to determine whether some of that invisible vapor will transform into falling rain. "To rain, or not to rain …" really is the question weather forecasters deal with daily.

Excerpted from The Complete Idiot's Guide to Weather © 2002 by Mel Goldstein, Ph.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.