Geography, climate, and environment

By total area (including its waters), Canada is the second-largest country in the world, after Russia. By land area alone, however, Canada ranks fourth, due to having the world's largest proportion of fresh water lakes. Of Canada's thirteen provinces and territories, eight share a border with the United States, and only two are landlocked (Alberta and Saskatchewan), with the remaining eight provinces and three territories directly bordering one of three oceans. Ontario and Quebec also send most of their shipping traffic through the St. Lawrence Seaway, which connects the Great Lakes to the St. Lawrence River, which flows into the Atlantic Ocean.

Stretching from the Atlantic Ocean in the east, along the Arctic Ocean to the north, and to the Pacific Ocean in the west, Canada has the longest coastline in the world, with a total length of 243,042 kilometres (151,019 mi), and occupies much of the continent of North America. Moreover, Canada's border with the contiguous United States to the south and the U.S. state of Alaska to the northwest forms the longest international land border in the world, stretching 8,891 km (5,525 mi). In addition to the U.S., Canada shares a maritime boundary with Greenland to the northeast and with the France's overseas collectivity of Saint Pierre and Miquelon to the southeast.

Canada is home to the world's northernmost settlement, Canadian Forces Station Alert, on the northern tip of Ellesmere Island—latitude 82.5°N—which lies 817 kilometres (508 mi) from the North Pole. Much of Northern Canada is covered by ice and permafrost; however, the future of the permafrost is uncertain because the Canadian Arctic has been warming at three times the global average as a result of climate change. Three of Canada's arctic islands – Baffin Island, Victoria Island and Ellesmere Island – are among the ten largest in the world.

Since the end of the last glacial period, Canada has consisted of eight distinct forest regions, including extensive boreal forest on the Canadian Shield; 42 percent of the land acreage is covered by forests (approximately 8 percent of the world's forested land), made up mostly of spruce, poplar, and pine. Canada has over 2,000,000 lakes—563 of which are greater than 100 km2 (39 sq mi)—which is more than any other country, containing much of the world's fresh water. There are also fresh-water glaciers in the Canadian Rockies, the Coast Mountains and the Arctic Cordillera.

Canada is geologically active, having many earthquakes and potentially active volcanoes, notably Mount Meager massif, Mount Garibaldi, Mount Cayley massif, and the Mount Edziza volcanic complex. The volcanic eruption of the Tseax Cone in 1775 was among Canada's worst natural disasters, killing an estimated 2,000 Nisga'a people and destroying their village in the Nass River valley of northern British Columbia. The eruption produced a 22.5-kilometre (14.0 mi) lava flow, and, according to Nisga'a legend, blocked the flow of the Nass River.

Average winter and summer high temperatures across Canada vary from region to region. Winters can be harsh in many parts of the country, particularly in the interior and Prairie provinces, which experience a continental climate, where daily average temperatures are near −15 °C (5 °F), but can drop below −40 °C (−40 °F) with severe wind chills. In non-coastal regions, snow can cover the ground for almost six months of the year, while in parts of the north snow can persist year-round. Coastal British Columbia has a temperate climate, with a mild and rainy winter. On the east and west coasts, average high temperatures are generally in the low 20s °C (70s °F), while between the coasts, the average summer high temperature ranges from 25 to 30 °C (77 to 86 °F), with temperatures in some interior locations occasionally exceeding 40 °C (104 °F).