Ice planets were cold planets with primarily icy terrain. Examples of these included the New Earth System's ice planet High Sierra. (COMIC: Doctor Who and the Dogs of Doom)
The Doctor visited several ice planets on his travels, including the ice-covered Calufrax, (TV: The Pirate Planet) Pella Satyrnis, where his fifth incarnation was stranded for five years, (PROSE: The Crystal Bucephalus) and the tidal-locked Svartos. (TV: Dragonfire)
Belazs believed that Kane came from one of the "frozen planets," as even Svartos was too warm for him, since his body temperature was -193 degrees below Celsius. (PROSE: Dragonfire)
The First Doctor once trapped the First Monk on an ice planet. (TV: The Daleks' Master Plan) The experience was so lasting on the Monk that after he escaped he lowered the temperature of his own TARDIS so that he never forgot the cold, and took his revenge by trapping the Seventh Doctor on the planet. (PROSE: No Future)
Isen VI was originally an ice planet where the Twelfth Doctor took Clara Oswald for skiing practice, but upon arriving they discovered it had been terraformed into a jungle planet. (COMIC: Terrorformer)