By the Blade!
The Dread Sea Dominions have not been charted in an exact way (today the science of geometry is practiced only by some scholar of the Syranthian Library), so it is difficult to estimate their actual size, but they certainly have a very wide range of different climates.
The northern reigns including the Caledlands, Northeim and the Cairnlands are cold, with winters lasting as long as six months and wide expanses of forests. The Troll Mountains, usually considered the northern boundaries of the world, are in the grip of ice for most of the year.
On the other hand, the lands facing the Dread Sea enjoy by far the best climate. Faberterra, Syranthia and Kyros have a temperate, Mediterranean climate with warm winters, long autumns and springs and generally hot summers. They have plants of all species including olive and fig trees, and the harvest there is always generous.
Tricarnia differs slightly from its neighbors. Despite being in the north, it is protected from the cold winds by the Brokenchain Mountains, so it has a temperate climate but it is quite damp. It has large, half-flooded rice fields that give the nation the aspect of a massive swamp which is always shrouded by thick fog.
Going south, the climate gets hotter. The area called the Horn, comprising the Fallen Kingdom, the Red Dunes Desert and the Ivory Savannah is scorching all year round, and the highest temperatures are reached in the desert. With the exception of oases, the vegetation mainly includes palms, cacti and other resilient plants. In the Ivory Savannah the main vegetable is the Bone Grass, a sturdy type of herb that in the summer takes on a pale color resembling that of bones.
Thanks to its position around the mouth of the Buffalo River, Caldeia enjoys a mild climate and its vegetation is similar to that of Kyros and Faberterra.
Going further south, the Lush Jungle and the Cannibal Islands have a tropical climate. Plants of every type and size grow in these snake-infested lands.
Moving east, Lhoban is an area of high mountains; it is quite cold with short, hot summers. Except for some lichens, very few plants grow in these lands but the valley bottoms are fertile, enjoy a mild weather, and yield excellent crops.
The old kingdom of Zandor, comprising Ekul, Jalizar and Valkheim, has the most varied climate.
Ekul is a cold, windswept desert with small oases. Here nothing stops the winds blowing from the Valk steppes. The only exception consists in the coastal regions, which are very fertile.
Jalizar has a continental climate which gets milder and good for the agriculture on the shores of the Drowned King Sea.
Valkheim, actually a part of the steppe, is always exposed to the winds and except for a short, hot summer, it is frozen all year round.