Change storms are supernatural weather phenomena that occur exclusively within the the Plain of Fear. The Lady speculated that the storms are the dreams of Father Tree - a speculation Croaker shared and elaborated upon as he described the change storms as "the nightmares of a God". Croaker, One-Eye, Goblin, and several others survived a change storm in The White Rose.
The White RoseEdit
Although the exact nature of the change storms is unknown, there are several occasions where Croaker observes the effect they have. The change storms seem to temporarily alter an individual's perception of reality (or reality itself), by either: showing what is hidden (as was the case when the demons Tracker and Toadkiller Dog briefly lost their human disguises); altering what already is (changing size and/or proportion); doing relatively nothing (as was the case with Croaker); or, causing other bizarre changes to objects and beings seemingly at random or according to the unknowable mind of Father Tree.
Creatures native to the Plain such as windwhales and mantas avoid change storms whenever possible. Windwhales, if unable to escape an approaching change storm, will instinctively land on the ground to minimize the possible harm.