Hyundai Ioniq charger: How does it deal with weather?

I think you'll find that most charging cables are rubber-insulated and not PVC insulated so they stay flexible in the winter temperatures. Try an experiment. Leave an indoors-only extension cord to -30C temperature and try to bend it. Try the same with your charging cable. The difference should be apparent.

I would be more worried about the battery at -30C temperatures. The battery needs to be heated up or else it'll self-destruct. The car has circuitry to prevent the self-destruction of the battery by heating it but it requires charge in the battery. Leave an electric car to -30C for month unused, the battery charge runs out and it can no longer keep the battery at an elevated temperature.

So, if leaving the car at -30C temperatures, the preference is to leave it plugged in. That way, the heating energy comes not from the battery but from the grid.