I would not use warm water let alone hot. They make ice scrapers for that kind of thing. BTW most cars will warm up in a few minutes and will start warming the window without any outside help. Letting the car warm up itself will mean the engine will also be a bit warmer by the time you move out into traffic.
Note: I is still best to drive the first few miles at reduced speeds (Avoid I-5 … OK during rush hour you can do I-5 as it will be nice and slow). You need to allow the other parts of your car, like the suspension system to warm up also before driving at freeway speeds.