The Inner Hebrides lie closer to mainland Scotland and include Islay, Jura, Skye, Mull, Raasay, Staffa and the Small Isles. The Outer Hebrides are a chain of more than 100 islands and small skerries located about 70 kilometres (43 mi) west of mainland Scotland.There are 15 inhabited islands in this archipelago.In 55 BC, the Greek historian Diodorus Siculus wrote that there was an island called Hyperborea (which means "beyond the North Wind"), where a round temple stood from which the moon appeared only a little distance above the earth every 19 years.This may have been a reference to the stone circle at Callanish.The main islands include Barra, Benbecula, Berneray, Harris, Lewis, North Uist, South Uist, and St Kilda.
In the Outer Hebrides the average temperature for the year is 6 °C (44 °F) in January and 14 °C (57 °F) in summer.
The Seaforths' royalist inclinations led to Lewis becoming garrisoned during the Wars of the Three Kingdoms by Cromwell's troops, who destroyed the old castle in Stornoway.
With the implementation of the Treaty of Union in 1707, the Hebrides became part of the new Kingdom of Great Britain, but the clans' loyalties to a distant monarch were not strong.
North of Dál Riata, the Inner and Outer Hebrides were nominally under Pictish control, although the historical record is sparse.
Hunter (2000) states that in relation to King Bridei I of the Picts in the sixth century: "As for Shetland, Orkney, Skye and the Western Isles, their inhabitants, most of whom appear to have been Pictish in culture and speech at this time, are likely to have regarded Bridei as a fairly distant presence.” Viking raids began on Scottish shores towards the end of the 8th century and the Hebrides came under Norse control and settlement during the ensuing decades, especially following the success of Harald Fairhair at the Battle of In the Western Isles Ketill Flatnose may have been the dominant figure of the mid 9th century, by which time he had amassed a substantial island realm and made a variety of alliances with other Norse leaders.