when super cold outside heater fan will not work

If it starts to work after about a minute or so this could be normal. Some cars don't have the blower work at first if it's really cold because it would just be blowing more cold air. It waits for the engine to warm up a little before working. Now if this happens in manual mode or the blower never comes on then some electrical testing is needed. You could start by checking fuses and checking for power at the blower motor. Alex