Minecraft wiki entry for Biome, associated text: These values can be used to determine the heights that snow generates at in different biomes. For example, windswept hills begin to generate snow at around y=120, due to their highland climate, as their temperature value is 0.2, the temperature affects only the transition from rain to snowfall. All the biomes in vanilla with a temperature above 0.95 (and by extent, all the dry biomes) are hardcoded to never have precipitation at any height or temperature. For example, savannas do not experience rain or snow due to their dryness. If a biome with a temperature above 0.95 is edited to allow precipitation through a data pack or mod, it simply behaves like a normal rainy biome.