in FH4 they swapped rally tires for snow tires in the winter season. as some have mentioned. this was the only off-road option in that game.
with the addition off-road tires in FH5, rally tires and snow tires became less off-road oriented. snow tires in FH5 have a terrible off-road rating, and exist as an alternative road tire that acts as merely a PI reduction tactic.
I would not recommend them for any of the snow in FH5, merely as an occasional way to force a car into a lower class