As there are no very high and large mountains in Finland, ice climbing spots are mainly frozen falls and streams. Korouoma Canyon near Posio is the best place for this winter outdoor activity. This is a long canyon with lots of icefalls and high cliffs to climb on. The difficulty level is quite high at some of the spots, and there are cliffs up to 100 m high. Forget about doing it on your own, unless you are very experienced and already have all the needed equipment. During guided ice climbing adventures you'll be taught how to survive in the Arctic.
The ice climbing season can change from year to year, as it is said to run from November through early April, but it is not always so. In December, at the very least, you'll definitely be able to enjoy your favorite activity.