Canada occupies a major northern portion of North America, sharing land borders with the contiguous U.S to the south and with the U.S. state of Alaska to the northwest, stretching from the Atlantic Ocean in the east to the Pacific Ocean in the west; to the north lies the Arctic Ocean.The population density, 3.5 inhabitants per square kilometre, is among the lowest in the world.The most densely populated part of the country is the Quebec City-Windsor Corridor along the Great Lakes and Saint Lawrence River in the southeast. To the north of this region is the broad Canadian Shield, an area of rock scoured clean by the last ice age, thinly soiled, rich in minerals, and dotted with lakes and rivers. Canada by far has more lakes than any other country and has a large amount of the world's freshwater.
In eastern Canada, most people live in large urban centres on the flat Saint Lawrence Lowlands. The Saint Lawrence River widens into the world's largest estuary before flowing into the Gulf of Saint Lawrence. The gulf is bounded by Newfoundland to the north and the Maritime provinces to the south. The Maritimes protrude eastward along the Appalachian Mountain range from northern New England and the Gaspé Peninsula of Quebec. New Brunswick and Nova Scotia are divided by the Bay of Fundy, which experiences the world's largest tidal variations. Ontario and Hudson Bay dominate central Canada. West of Ontario, the broad, flat Canadian Prairies spread toward the Rocky Mountains, which separate them from British Columbia.
In northwestern Canada, the Mackenzie River flows from the Great Slave Lake to the Arctic Ocean. A tributary of a tributary of the Mackenzie is the South Nahanni River, which is home to Virginia Falls, a waterfall about twice as high as Niagara Falls.
Northern Canadian vegetation tapers from coniferous forests to tundra and finally to Arctic barrens in the far north. The northern Canadian mainland is ringed with a vast archipelago containing some of the world's largest islands.
Average winter and summer high temperatures across Canada vary depending on the location. Winters can be harsh in many regions of the country, particularly in the interior and Prairie provinces which experience a continental climate, where daily average temperatures are near −15 °C but can drop below −40 °C with severe wind chills. In non-coastal regions, snow can cover the ground almost six months of the year (more in the north). Coastal British Columbia is an exception and enjoys a temperate climate with a mild and rainy winter.