Temp in biomes isn't measure by a degree, but by a Y: coordinate. I think its 90, but don't quote me on that.
It wont snow above y90 or any other y level in, plains, desert, Mesa, jungle, savannah, ocean, river, forest, roofed forest, birch forest and mushroom island. There are more... Biomes that will snow above y90 extreme hills, ice plains, and most "colder" biomes
I made a public ice gen at 8666 on smp4, and it's been working fine. And I believe ice gens at 128+ but not entirely sure.