Canada occupies most of the northern portion of North America, sharing land borders with the contiguous United States to the south and with the US 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. Since 1925, Canada has claimed the portion of the Arctic between 60°W and 141°W longitude; this claim is not universally recognized. The northernmost settlement in Canada (and in the world) is Canadian Forces Station (CFS) Alert on the northern tip of Ellesmere Island—latitude 82.5°N—just 817 kilometres (450 nautical miles) from the North Pole. Canada is the world's second-largest country in total area, after Russia, and the fourth largest in land area, after Russia, China and the United States.
The population density of 3.5 people per square kilometre (9.1/mi²) 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 in the world and has a large amount of the world's freshwater.
In eastern Canada, the Saint Lawrence River widens into the Gulf of Saint Lawrence, the world's largest estuary; the island of Newfoundland lies at its mouth. South of the Gulf, the Canadian Maritimes protrude eastward from 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.
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 Prairie provinces, where daily average temperatures are near −15°C (5°F), but can drop below -40°C (-40°F) with severe wind chills. Coastal British Columbia is an exception and enjoys a temperate climate with a mild and rainy winter.
On the east and west coast average high temperatures are generally in the low 20°C (68 to 74°F), while between the coasts the average summer high temperature range between 25°C to 30°C (78 to 86°F) with occasional extreme heat in some interior locations exceeding 40°C (104°F). For a more complete description of climate across Canada see Environment Canada's Website.