That's just the additional energy used. Battery performance itself is directly affected by extreme temperatures.
How would an electric vehicle perform in MN in the winter, or Phoenix in the summer?
In MN?
Tesla will do very well.
http://www.youtube.com/watch?v=XZ5PqPeOPT0
Tesla Model S cold weather testing in Norway.
The batteries are cooled in hot weather and warmed in cold weather.
Will also do very well in Phoenix but don’t have a video.
Tesla is not Fisker.
It is a serious engineering company not an exterior design and marketing firm.