That Time of Year

What is it about this time of year that makes me constantly feel like I am on the cusp of getting sick? I have the sore throat that waxes and wanes, slight achy-ness, constant sneezing and a prevailing, overwhelming exhaustion that doesn't seem to go away no matter how much sleep I manage to get. Of course it could possibly have something to do with the warm days and the cold nights. You know, it's probably never that good to go to bed with the windows wide open, only to wake up at 3 AM shivering to find that it's 30 degrees in my bedroom. Yeah, not good.