Hi There Liquid,
The winter months are just awful for me. I have to bundle up or I pay the price for it the following days. My jaw tension is tied in with tension in my neck and shoulders so whenever I am out in the cold I tend to tense up my neck and shoulder region and that tension eventually runs back up into my jaw muscles and makes them tighter. that is the best way I can describe it. Everything seems to tense up in the cold. I try to take hot showers and baths more frequently during the cold months to combat the muscle tension, and it REALLY helps. More reason to take relaxing bubble baths! whoo hoo!
Im sorry, at this point in time I don't have too many issues with my sinuses although I do get pain and throbbing in my upper teeth sometimes, so someone else will have to elaborate on the sinus issue for you.