Car will not heat battery unless battery is below -7C if car is unplugged. If the the car is plugged in then it's below 10C. This is visible on the canbus/obd2. It's much higher when plugged into a supercharger.
Edit: You'll see the snowflake loss, even before the snowflake. There's just a point past which the icon will come up, but it'll affect range before that. You'll see that as percentage won't go down but rated miles will.
Edit 2: From my experience that -7C heating when unplugged is only when car is on/in drive. If parked it won't even do that much. (If car is plugged in it's a different matter).