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April Showers
Thu May 22, 2003
Listen in RealAudio 
April showers bring May flowers, so the rhyme goes. April is the transitional month for the
character of American precipitation, particularly in the interior states. From April until
late autumn, rain across the country mostly falls as showers from convective clouds.
So, while we hide from April showers, let's look at some rainfall trivia.
Raindrops have diameters larger than 1/50 inch but can reach about a quarter inch before
breaking into smaller drops. Typical diameters are about 1/10 inch across.
Larger drops mean more accumulation. Downpours with quarter-inch drops will bring down 500
times more water than the same duration rainfall with drops one-sixth the diameter, 0.04
inch.
Typically, raindrops fall around seven miles per hour in still air, but this depends on
several factors, especially their size. Large drops not only contain more water, they also
fall faster, as quickly as 18 miles per hour.
One inch of rainfall is the amount covering an area to one-inch depth if none soaked in. If
you don't think an inch of rain is much water, one inch of rain equals 5.6 gallons or
approximately 1 billion raindrops over a square yard. Distributed over an acre, that totals
27,000 gallons weighing 113 tons.
The most rain in a day fell on Alvin, Texas, in July 1979: 43 inches. In 1956, Unionville,
Maryland received 1.23 inches of rain in one minute. And finally, in 1953 in Leicester,
Massachusetts, it rained toads!
Thanks to our contributing writer, meteorologist Keith Heidorn. Our program is funded by
Subaru of America and The National Science Foundation.
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