I purchased an '02 Durango 4.7 while in the military and owned it several years after. The SUV saw summers and winters in the Southeast (where I bought it), Midwest, Northwest, and eventually landed in my home state in of Texas after I discharged.
I never noticed a lick of different in the performance or reliability across the state and seasons. YMMV
With my previous vehicle - 1989 Honda - I didn't notice a significant change. That was because the older A/C compressors required more of the engine's power than the ones in use today. I can still feel a difference in performance when using the A/C in my 2012 Mazda, but not as much as in previous vehicles.
I lose at least 5%, and maybe 10% during the winter. Hard to tell, though, how much is from the gas and how much from the cold starts. On long highway trips, generally 5% less in winter.