What is the lowest dew point ever recorded in Chicago and when did it occur?
— Robert Skurski, Chicago
The dew point is the temperature to which air must be cooled to reach saturation; when this occurs the relative humidity is 100 percent. Once air is saturated, temperature and dew point can rise or fall together, but the dew point will never be higher than the temperature.
Chicago climatologist Frank Wachowski reports the city’s lowest dew points all occurred with its lowest temperatures. The record low dew point of minus 39 was on Jan. 20, 1985, in conjunction with Chicago’s all-time lowest temperature of minus 27. Runners-up: dew point of minus 38 on Jan. 10, 1982, with a temperature of 26 below; dew point of minus 37 on Jan. 16, 1982, with temperature at 24 below.
Snow developing across eastern Iowa late this evening headed into Illinois. As the clipper system approaches snow has developed across portions of eastern and is spreading into northwest Illinois. The visibility at Waterloo, Iowa has dropped to 3/4 mil as the snow increases in intensity while dropping to 2 miles at Dubuque.
Current forecasts appear on track with the snow spreading across the Chicago area from west to east in the predawn hours.
Winter Weather Advisory in effect for much of the Chicago Metro area from midnight to 10am Wednesday
Snow will overspread northern Illinois from the west and northwest overnight reaching the Chicago between 4am-8am just in time to play havoc with the Wednesday morning commute. While snow totals will not be excessive with general 1-3 inch totals expected, the combination of the falling snow, gusty winds and temperatures near 20 will create slippery driving conditions.
The snow should exit the area by mid or late morning followed by strong west-northwest and falling temperatures.
Thanks to Evelyn Landa for this great shot of her dog Lango decked out in Bulls attire.
Thanks to Walt Willing for this great shot taken at the Highland Park Water Plant.
THE WARMEST OF TIMES
Taken in my backyard in Boca Raton, Florida
where it’s been over 80 every day this week 70′s at night.
THE COLDEST OF TIMES
Taken in DeKalb County
Brad Hruza sent us this holiday scene complete with snow from Elburn.