Are UV rays really more powerful on cloudy days?
Dear Cecil: Here in Japan, muggy summer marks the annual appearance of parasols, long gloves, and enormous hats, all to protect against dreaded UV rays. Yet rather surprisingly I see more of this on cloudy days than on sunny days. When I asked a friend why, she said it was because UV rays are more powerful on cloudy or hazy days and because people were duped by Mother Nature into believing that dark skies equals less UV exposure. Are clouds really UV magnifying glasses? Or do the Japanese need one fewer old wives’ tale? — Kirk Andersen, Kyoto I can’t really blame you for not buying this one, Kirk. Off the bat, the notion that ultraviolet radiation is worse on cloudy days sounds a lot like one of those truly moronic bits of “counterintuitive” folk wisdom that often catch on (see, e.g., cold water boils faster than hot). And what with Japan being home to some very serious devotees of neo-Victorian fashion (the curious can go search “gothic lolita”), a reasonably skeptical gaijin like you
