History and specifics
Until the 2260s, Floe I was the homeworld of a civilization of humanoids known as the Floes. At the time the Floes joined the Federation, Floe I was class M with a temperate climate supporting trees, bushes, flowers, and goat-like mammals.
The planet's orbit around the star Floe began to expand outward, cooling its atmosphere and dooming the planet to an eternal ice age. By the 2260s, its population was reduced to one large underground city, and Floe I was regarded as the coldest planet in the Federation.
In 2266, the Federation sent the starship USS Enterprise to conduct a population survey of Floe I. The landing party discovered a desperate dictatorship and a slave revolt, with decreasing surface temperatures condemning the society to extinction within a few days. (TOS comic: "Ice Journey")