Heater fan

Temperature extremes can cause weird things, especially if a part is ready to fail anyway.

What you'll need to do is narrow things down by first checking the fuse to make sure it's good and seated tightly.

Also, are you using a manual or automatic setting? If you are using automatic, then there's probably a "Cabin Temp" sensor that is failing.

Next, remove the fuse and use a test light or voltage meter and insert the leads into the contacts where the fuse goes. Turn on the blower motor in manual mode.

If the light comes on or you read voltage, then the wiring is good and the blower motor is bad. If no light or voltage, then the problem is in the control unit, probably a sensor.