8. Flu season is upon us, and Health Services decided we could all use a humidifier.
9. Due to budget cuts, the Art Department had to sell all its welding equipment and start relying on the dragon who lives in the caves beneath the Hill.
Really though, the reason why you might see fog coming out of grates around campus is the same reason you can see your breath when it is cold out. Basically, the warm air from inside can hold a lot more moisture than the cold air outside, so when the air circulates back outside, the water vapor cools into liquid and forms tiny droplets that we see as fog.
It’s kind of a boring answer — I’d much rather believe in the friendly, industrious dragon that definitely lives under FAC.