Dear Tom,
During our recent subzero outbreak, my digital thermometer read -0.6(degrees). Would the National Weather Service report this as 0(degrees) or -1(degrees)?
Jeff Siebert, Lindenhurst
Dear Jeff,
The temperature rounding system used for reporting and climatological purposes by the U.S. meteorological community is quite simple. If the tenths digit is 5 or higher, the reading is rounded to the next highest number, no matter if it is positive or negative. If the tenths digit is 4 or lower, the degree value will remain unchanged. A temperature of +/- 5.6(degrees) would be recorded as +/-6(degrees), while a reading of +/-22.4(degrees) would go down in the books as +/-22(degrees). This system results in a built-in 0.8-degree variance in what the exact temperature may actually be. A temperature reported to the media as 90(degrees), when read to the tenth of a degree could in fact, be anything from 89.6(degrees) to 90.4(degrees).
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
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