Saturday opens with muggy 70° dew points and relative humidities flirting with 100%—an indication the atmosphere is saturated with moisture. That moisture fueled overnight downpours and had reduced visibilities late Friday to an eighth of a mile at times near Waukegan. For areas adjacent to Lake Michigan, fog vulnerability is a major issue because air and water temperatures equal the dew point—and the dew point marks the temperature at which fog forms. With only limited wind Saturday, the prospect of sweeping clouds and haze from the sky with a push of dry air is low. That’s why it’s a good bet the first day of the Air and Water Show is to feature extensive haze, a good deal of cloudiness, and in some lakeside locations, the potential for fog.
Temperatures, as a result of all the moisture in the air, remained above 70° Friday for the 30th time this year at Midway—nearly twice the normal of 16 to date. Only seven years since 1928 have logged more 70°-plus overnight lows.
--By Tom Skilling, WGN-TV Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
