Thetan’s weather is based on the location and interaction of hot and cold air regions and the atmospheric circulation created by the Golden Winds (easterlies) and Barrier Winds (westerlies). The Golden Winds blow from the northeast, while the Barrier Winds blow from the southwest. The Barrier Winds steer storms from west to east across Thetan. The Endless Spines serve as a natural rain shield, resulting in lush forests on the western side of the mountain ranges.
Thetan’s ocean currents are determined by a combination of its weather, Thetan’s easterly rotation, and the gravitational forces of Thetan’s two moons: Perun and Veles. The currents of Shaldwin’s Ocean and Shining Sea flow in a clockwise direction along the eastern coast and Platinum Bay. The currents of the Barrier Sea flows in an anti-clockwise direction along the Caru Coast. The currents of the Crown’s Waters flow in an easterly direction, eventually turning in an counter-clockwise direction to the north along the Crown’s Coast.
Stretching east from the Dragon’s Horn, the Crown’s Coast is dominated by frigid air masses. Cold weather is long and severe, with a short reprieve during Fire Pass. Moderating winds keep the temperatures warmer on the coast than they are at the base of the Crown of Thetan mountain range.
The climate of the mountains of the Crown of Thetan changes rapidly, becoming even colder in higher altitudes. The peaks of the mountains are snow-capped throughout the year. Snows that develop further down the mountains melt during Rebirth and Fire Pass, though these waters do not flow into the Desert of Regret.
Along the western edges of the Crown’s Coast, rainfall is abundant. Persistent low clouds and mild weather is common throughout Cold Fall and Fire Pass. Although there are periods of snow, most precipitation is in the form of rain.
The lands of central Ramsden are called the Aduyu’Orun or “Country of Horses.” This area is typified by its dry climate, caused by air masses being blocked by the Borderlands, Crown of Thetan, and Endless Spines. This allows cold air masses to dominate in Cold Fall while continental air mass is dominant during Fire Pass. A small amount of rain falls during Fire Pass. Temperatures range widely. Fire Pass is warm to hot, and temperatures can be very cold during Cold Fall.
The Borderlands are semiarid, with shrub grass on their southern periphery. They are completely barren where they meet the Desert of Regret. Temperatures are extremely hot during Fire Pass and equally cold during Cold Fall.
The Desert of Regret has a dry arid desert climate. It has light winds, allowing for the evaporation of water in the intense heat. The desert is completely surrounded by the mountains of the Crown of Thetan and the Borderlands, which prevents moisture from reaching the desert. The Desert of Regret has the hottest temperatures of any region of Thetan. Even temperatures during Cold Fall are harsh. Conversely, the night time temperatures can be unbearably cold. Only the elves, with their natural resistance to intensely hot temperatures – a evolutionary product of the altered environment – can endure the Desert of Regret for extended periods.
The climate of the Endless Spines is less extreme than that of the mountains of the Crown of Thetan. The Endless Spines are much older, its ridges are shorter, and the terrain is less rugged. The peaks of the mountains are snow-capped, though typically only in Descension, Cold Fall, and early Rebirth. Snows that flow from the Endless Spines feed the rivers and lakes of the Inner Plains, the Tarsal Coast, and the Droch Marsh.
The Valley of Life, Inner Plains, the Tarsal Coast, and the Crown’s Reach have temperate climates. There are significant climate changes between the seasons of Cold Fall and Fire Pass. Daily temperatures also change often. Abundant precipitation falls throughout the span. It is increased in Fire Pass – especially in the southern regions – by warm air masses. Cold periods during the seasons of Cold Fall are caused by cold air masses from the north moving towards the south.
The Droch Marsh is known for mild weather during the season of Cold Fall, while warm and humid throughout the rest of the span. Thunderstorms are common during the afternoon and evening hours of Fire Pass.
The Field of Blood’s climate is immune to Thetan’s natural weather phenomena. It is a barren, arid wasteland with no known water sources. Its weather and climate appear to be tied to influence from the negative energy plane.