The range percentage reduction predictions need a lot more detail.
I have a 10km each way commute, and have seen as low as -32c.
On a -20c morning if I don't preheat the car plugged in I have seen energy use nearly triple but then begin to fall but still be over double when I park. Initial heating is a huge hit and short trips make this a last most of your driving time. On a longer drive at your temps you might only see a 10% range reduction, but on short drives will see consumption spike much much more.
Range wise you can mitigate this with preheating while plugged in, granted you are using the energy, just not from the battery so it doesn't show up on your dash.