Absolutely, the scenting conditions are better in the fog. The only issues I have experienced with foggy mornings are... typically to have a heavy fog, you have light wind to no breeze at all and that can be an issue because you wont get much of a scent cone. Also, in my experience, quail don't like to flush in the fog. I would guess it's because they can't see above themselves (for predators), but on really foggy mornings, birds tend to run and stay on the ground.
cold foggy mornings with a breeze, just as the fog is lifting... dogs will be on fire and that will put some birds on your gun for sure!