FOG formed early Wednesday in some areas surrounding Chicago.

Most vulnerable to fog formation are areas away from the “heat” of the city and Lake Michigan.

In these areas, nighttime cooling take temps down to the dew point, the temp at which the air becomes saturated with moisture.

Here’s another way to think about the dew point. It’s the temp at which the relative humidity hits 100%. (See the dew point map I’ve included–and you can see the way moisture out of the Gulf of Mexico covers much of the eastern U.S.).

The photos a number of you shared with me Wednesday morning, are lovely! THANKS for taking the time to do so!!