Heat the catenary.
It could be necessary to heat the overhead wire at some locations during extra tough weather conditions. Sometimes it is sufficient with the heat generated by the traction current why a frequent traffic is preferable from this aspect. Sometimes an additional reactive current is used to prevent or reduce the build up of rime on the contact wire.

So the Nordic countries indeed do it, too, albeit no details are given.

_{*Lunatic*, n.
One whose delusions are out of fashion.}