Below is a picture from our City Cam early on Saturday morning.  Fog can form at anytime, but is most common during the early morning….that is usually when temperatures are at the low point for the day.  If temperatures drop enough, they can get close to the dewpoint.  The dewpoint is the temperature at which the air can no longer hold moisture, and that’s when you start to see fog.  Even if the temperature is not exactly equal to the dewpoint from the official weather service station , it may be equal in other spots which is why you can see some fog in the picture below. –Pete Mangione