Temperature definately affects mileage! Oils and greases that lubricate wheel bearings, u joints and axles will cause more parasitic drag which eats more fuel. Also, the further north you got the more mountainous the terrain and even with coasting downhill, the uphill sections will use more as well.
I bought mine end of September so haven't had a lot of post break in warm weather miles BUT... I have noticed a drop in daily average when the weather is coldest. Went from 15-16 to 14-15. I attribute that to more idling for morning warm up along with cold lubricants!