Dear Tom,
How often do you refigure average daily temperatures? For instance, if we have an unusually warm winter, how does that affect our average temperatures?
Eloise Berg
Dear Eloise,
By international agreement, temperature averages (and other climatological stats) for all cities and locations worldwide are based upon a 30-year period, currently 1971-2000, and the averages are recalculated every 10 years.
New temperature averages, derived from the next qualifying 30-year period, 1981-2010, will be calculated eight years from now. That means a mild winter such as the one just ended will not enter into Chicago’s temperature statistics until 2011.
The World Meteorological Organization, a special agency within the United Nations, establishes those international standards and 185 member nations, including the United States, adhere to them.
———-
Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
Send your questions to:
ASK TOM WHY, 2501 Bradley Place, Chicago, IL 60618
e-mail: asktomwhy@tribune.com
