Ymireans hold that at the northmost place in the world sits a giant frost god (called Boreas in Cargandom and Aule by the Fraegings) and exhales cold winds, while at the very southmost on the world's rim sits a giant fire god (Auster to the Cargans, Muspell to the Fraegings) blowing scathingly hot winds northwards.
What is securely known is that cold winds from the north and hot winds from the south are the main causes of shifts in temperature, and that the relative strength of these winds cause the cycle of spring, summer, autumn and winter. In winter, the north wind predominates, in the summer it blows mostly from the south. The cold northern winds also tend to blow more strongly widdershins, while the warm winds of the south tend to seek a deasil path more often.
The sun also gives heat to the world, but in lesser proportion than the northern and southern winds, governing primarily the temperature difference between night and day, though the sun also glows stronger in the summer and weaker in the winter, some say it is banked when Aule's breath grows strong enough to reach it.