The landscape of South Karelia contains a great deal of water. Additional geographical elements are forests, fields and marshes. A large distinct characteristic of the area are the Salpausselkä ridges that were created during the Ice Age. They can be found, for example, on the southern shore of Lake Saimaa and on Kyläniemi, in the centre of Lake Saimaa. Salpausselkä ridges divide the province into various parts, in the longitudinal directions. The first Salpausselkä ridge dams the Lake District, on the northern side. The southern side has more fields.
The surface area of South Karelia is about 20% water. Lake Saimaa’s waters flow down River Vuoksi into Lake Ladoga. The waterways of Hiitolanjoki are located in the eastern part of the province, the main lake of which is Lake Simpelejärvi. In the West, the waters once again flow along the Lake Kivijärvi route into the Kymi River. The majority of the province’s waterways are barren and have clear waters.
75% of the land area of South Karelia is forest. As a result of the strong history of wood processing, the trees in the region’s forests are of different ages and for the purpose of forestry. The most barren heaths can be found on the ridge areas of Salpausselkä and elsewhere, where the most general types of trees are pines. The lushest forest areas are located in the northern part of the province, where the portion of grove-like forests may represent up to more than half of the forest land.
Only 17% of the forestry land in South Karelia is taken up by marshland, which is, noticeably, a great deal less than elsewhere in the country.
South Karelia belongs to the southern boreal vegetation zone. The fauna of South Karelia has its origins in the species of the south and east. The moose population is vibrant. The large carnivores of Finland are concentrated towards the eastern border, where bears and wolves may also be encountered. These large beasts are, however, very rarely seen.
Due to the eastern influence, the bird life is interesting. For example, many night singers are very common in this area. During the spring and autumn, birds that nest in the Russian Arctic tundra often migrate and pass over and through the province.
Lake Saimaa in South Karelia is home to a small number of highly endangered Saimaa ringed seals, totalling, approximately, 300 individuals. Protective measures have been taken to save the Saimaa ringed seals.
The climate of South Karelia can be characterized as being continental, in particular, in the north-eastern part of the province, but further south, the influence of the sea can be felt. Also, Lake Saimaa equalizes temperature differences and increases the humidity levels.
During the summer, the average temperature is 17 °C, which is the highest in the whole country. Also, the annual rainfall is the greatest in the country. Permanent snow cover arrives, on average, during early December.