Weather: Playing the Odds

Playing the Odds

You can continue to narrow down the forecast still more by working with climatology. For example, it rains or snows in New York City an average of 121 days each year, or on about one third of each year. If you predict that the weather will be good each day, your forecast will be correct 67 percent of the time. You can forget about calculus, weather maps, satellite loops, radar—all of it. Just predict that it will never rain in New York, and you'll be right two thirds of the time. And what's wrong with 67 percent accuracy? If you were a baseball player and hit .670 every season, you wouldn't just be put in the Hall of Fame, a new hall of fame might be built in your honor!

Of course, areas other than the stormy mid-latitudes will provide an even higher accuracy rate. In Los Angeles, rain only falls about 10 percent of the time. If you say it will never rain in southern California, you'll be correct 90 percent of the time. Who needs to listen to the evening weather? The following figure lists the percent of the time that precipitation normally occurs at the various major cities. Find the city nearest you and impress your neighbors and relatives.

Percentage of rainy days.

City	% of days with precipitation
Atlanta, GA	32%
Birmingham, AL	32%
Boston, MA	35%
Buffalo, NY	46%
Chicago, IL	34%
Denver, CO	24%
Detroit, MI	36%
Hartford, CT	35%
Houston, TX	30%
Kansas City, MO	28%
Los Angeles, CA	9%
Miami, FL	35%
Minneapolis, MN	31%
New Orleans, LA	31%
New York, NY	33%
Philadelphia, PA	32%
Phoenix, AZ	9%
San Diego, CA	11%
Seattle, WA	44%
Washington, DC	31%