Make sure your windows are clean.
Foggy windows can be a result of using your air conditioner. A/C's are great for clearing windows of fog, but the condensate on the window collects on the fins of the evaporator in the a/c. Next time you use the fan, even with heat selected, the moisture is blown back into the car and presto the windows fog up, especially in moist cool weather conditions.
Running the a/c all the time will keep your windows clear.
There is a drain pipe for the moisture to drain under the car, but not all of it drains completely.