You might go to a lighter oil in that case... at least for the colder months. It's quite common to think that a thicker oil in a manual tranny is better, but it really isn't. 10W-30 or 10W-40 are good, all weather oils for the transaxle while 20W-40 and straight 30 are better used in much hotter climates.
Not sure what oil you're running, just wanted to throw this out there, FYI.