Igloos are shelters constructed from blocks of snow, generally in the form of a dome. Although igloos are
usually associated with all Inuit, they were mosttly constructed by people of Canada’s Central Arctic and Greenland’s Thule area. Other Inuit people tended to use snow to insulate their houses which consisted of whalebone and hides. Snow was used because the air pockets trapped in it make it an insulator . On the outside, temperatures may be as low as −45 °C (−49.0 °F), but on the inside the temperature may range from −7 °C (19 °F) to 16 °C (61 °F) when warmed by body heat alone.
The snow used to build an igloo must have sufficient structural strength to be cut and stacked in the right way. The best snow to use for this purpose is snow which has been blown by wind, which can serve to compact and interlock the ice crystals . The hole left in the snow where the blocks are cut from is usually used as the lower half of the shelter. Sometimes, a short tunnel is built at the entrance to reduce wind and heat loss when the door is opened.