Sorry for the stupid question!
Most Helpful Guy
I wear long underwear year-round - even in summer.
So if you are cold, just wear it - no matter what others do.
Most Helpful Girl
Under your clothes. I don't know if you're going to need them until there's snow on the ground, but then again I grew up in Canada. If you're going to be inside most of the day, I don't expect you'll use them unless it's very drafty where you live/work/study.