Karafuto was a former Japanese prefecture in the southern part of Sakhalin island, from 1905 to 1945.
The Karafuto Prefecture incorporated several smaller islands.
Karafuto was a very mountainous area. Its highest mountain was Mount Shisuka.
Owing to the influence of the raw, foggy Sea of Okhotsk, the climate is very cold. At Dui the average yearly temperature is only 0.5°C (January -15.9°; July 16.1°), 1.7° at Kushunkotan and 3.1° at Aniwa (January, -12.5°; July, 15.7°). At Mamiya near Dui the annual range is from 27° in July to -39° in January, while at Rūtaka in the interior the minimum is -45°C. The rainfall averages 570 mm. Thick clouds for the most part shut out the sun; while the cold current from the Sea of Okhotsk, aided by north-east winds, brings immense ice-floes to the east coast in summer.
During the winter, the Sea of Okhotsk turns to ice, rendering the northern coast impassable to marine traffic, and halting the lucrative fisheries there until the thaw.