snow spawns on railroads only in winter biomes, it doesn't spawn on mountain peaks

you need to change the rate at which snow accumulates on the rails

I will write differently

maybe so. Now it's not related to the Serene Season mod

I mean that it does not accumulate exactly on the mountain peaks. It is available in winter biomes.

the seasons mod goes quite quickly, either change the length of the seasons or change the snow accumulation rate

What mod is putting snow on the mountain peaks?

vanilla

and "serene season" add snow in most biomes in winter season

Ok, if minecraft is not marking it as a "snow" biome, IR can't detect that. Serene season compatibility is on the long term roadmap

ok, but https://minecraft.fandom.com/wiki/Snow#Post-generation

Here are additional options for generating snow by height in different biomes, maybe it is possible to add these checks for rail sections