The Doors of Oerth
Oerth is the name of the planet on which the World of Greyhawk campaign setting is located. Oerth has an axial tilt of 30 degrees, which should cause greater extremes of temperature in different seasons but wizardly and divine magics are used to shift weather patterns to be more favorable to the populace. Some regions of the world are known to exhibit strange weather phenomena such as black snow fall, strange tidal occurrences. Planar instability and dimensional gates have a significant impact on the weather in some areas and persistent magical effects are also cited as the reason for the environmental hostility large sections of the landscape.