The Twilight Forest‘s glacier biome, home to the Ice Queen boss, rains instead of snows, and if you have Fabric Seasons installed, the entire glacier will melt, even if Fabric Seasons is not configured to do anything in the Twilight Forest.
This is because Fabric Seasons causes all ice blocks to melt when they are in a biome with a temperature above 0.15. The Glacier biome has a temperature of 0.8. This is probably unintended, as the surrounding snowy forest is 0.09, so this datapack just changes the temperature to 0.08.
On servers, this can cause some lag as the ice melts. And for clients this can cause huge FPS drops if you have a water visuals mod like Effective installed.
With this datapack loaded, the Glacier biome snows instead of rains, and even with Fabric Seasons installed the ice will not melt.
To use, add to your world datapacks folder or load automatically with a datapack loader like Paxi