I think I'm slowest in Winter because I have to control my breathing to avoid excessive mucus buildup. When you breath as quickly as you can through your mouth, your body compensates by moving extra mucus.

In the summer time, I can breath more quickly and I don't have to limit myself so much.

Of course the lube would have an effect. The shrinking and enlargening of certain materials do make a difference though I doubt it's much when you are in the "normal" temp range of 35 to 80 degrees F.