Lead acid car batteries have the same issues, and I'd imagine that car battery shops are busy this time of year, and go into hibernation in July.

The electric cars are supposed to regulate their battery temperatures (heat or cool as needed). It might help if they are on a float charge at night so they can have power heating.

My guess is the Tesla range was shortened because the guy was using electric resistance heating in the car (and perhaps for the batteries).

Ideally, though, a car will also recover heat from the motor for use.