Rùm rest of the British Isles and Scotland, Rùm features a strongly maritime climate with cool summers and mild winters. There is a MetOffice weather station at Kinloch providing long term climate observations. The main range of hills on Rùm are the Cuillin, usually referred to as the "Rùm Cuillin", in order to distinguish them from the Cuillin of Skye. They are rocky peaks of gabbro, forming the Rum layered intrusion. Geologically, Rùm is the core of a deeply eroded volcano that was active in the Paleogene era some 60 million years ago, and which developed on a pre-existing structure of
Cuillin the summits had no recorded name prior to this period, although names for corries and other features were in existence. Many of the summits are thus named after early climbers such as John MacKenzie (Sgùrr MhicChoinnich), Alexander Nicolson (Sgùrr Alasdair), and Norman Collie (Sgúrr Thormaid). The Cuillin now consists of two estates divided by Glen Sligachan. The hills on the west side of Glen Sligachan (the Black Cuillin) remained the property of Clan MacLeod despite the long history of conflict between them and Clan MacDonald. The earliest formal record of MacLeod ownership was in a land grant from the Crown