DO you have a cabin filter? It acts as a protective cover of sorts for the HVAC system. I agree that you may have some ice in the passage that is preventing the fan from moving. I would try to get the car to a warm garage or heat up the interior somehow. If you can, I would open up the cowl on the pass side and look down there. I would also put the fan to Off before the motor fries trying to overcome the resistance.

On the other hand, the cold may just have claimed it. But usually the fan squeaks a lot before just quiting. Since the fuses are good, the only other possibilty is a loose wire due to thermal contraction - but that's iffy.