The weather can truly affect your mpg (this is true on any car). I'm in Sacramento, CA, but this winter has been pretty cold for us. (30-50 in the AM, 50-55 in the PM). In the spring, summer, and fall, I averaged 50mpg and 600-625 miles/tank. Since November, I've average about 45mpg or so and about 500-525 miles/tank. Still nothing to bauk at! It is most noticable on hybrids since we can't get the most use out of AutoStop and "EV" mode until the car is warmed up. I know I'm noticing at least 3-4 miles before the warmup, vs 3/4 mile when the temps are warmer. I mainly drive 7 miles in the morning to work through the city and about 5 stop signs and 10 traffic lights (a few more if I have to drop my daughter off at school). Throughout the day I drive to computer jobs ranging from 5-25 miles away. Next winter, the drive to work will only be 3-4 miles so the car will be just warming up as I pull into work! Looks like I'll be getting a block heater!!!