They have winter tyres and summer tyres.
In the far North where I work you swap between them at the change of seasons. Winter tyres are soft and studded (you also get non studded ones, but not advisable there), but they wear extremely quickly and the studs wear grooves in the tar in summer. we also use chains once off the main roads.
There is no difference in the speed limits, or the speeds that they travel between summer and winter, and the roads can be up to 50cm deep in compacted snow and ice.