Dear Tom,
When it snows overnight, which day gets “credit” for it? Let’s say it starts snowing at 9 p.m. and doesn’t end until noon the next day.
Doug Memler, Winfield, Ill.
Dear Doug,
All weather events are measured in 24-hour increments, midnight-to-midnight, in Local Standard Time.
When precipitation (like rain or snow) extends across midnight, precipitation logged on the first day is the amount that falls up to midnight at the end of that day and precipitation logged on the next day is the amount that falls after midnight at the beginning of the second day.
Snow beginning at 9 p.m. and ending at noon the next day is broken into two parts, with midnight as the separation point. If four inches of snow fell, one inch before midnight and three inches afterward, it is logged as one inch on day one and three inches on day two.
———-
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.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
