The weather slows your movement as you freeze to death. You need to look for equipment to protect you from the cold.
Freezing Weather was a debuff caused by being in a blizzard in Death Mode without any form of Cold Protection. It reduced the player's movement speed and acceleration by 0.0167% every second the player was active with this debuff. After 30 seconds, the player would be inflicted with the Frozen debuff, and would be killed 3 seconds later.
The timer raised twice as fast while the player contacted water. The debuff was removed as soon as the player exited the Snow biome or obtained Cold Immunity. However, the decreased movement speed would slowly be removed over time rather than instantly.