Hot Flashes: Normal Or Should I Be Concerned?

Elizabeth
Been having hot flashes all week. On and off, mostly in the afternoon to early evening, then again during sleep. I'm only early 20s, so I don't think it's menopause, and I've read that hot flashes can happen at any time, but how many is too much?
It's been cold where I live lately and inside buildings are quite warm. Could sudden changes in environment be triggering them?