Ontario

Ontario is Canada's southernmost province, sitting in the central part of the country. It ranks as the second-largest province by total area, behind only Quebec, and is the fourth-largest jurisdiction among all Canadian provinces and territories. The province is home to both the national capital, Ottawa, and Canada's most populous city, Toronto, which also serves as Ontario's own capital.

With over 14 million residents as of the 2021 census, Ontario is the most populous province, accounting for roughly 38.5% of Canada's population. To the west lies Manitoba, to the north Hudson Bay and James Bay, and to the east and northeast Quebec. Its southern border touches several U.S. states: from west to east, Minnesota, Michigan, Ohio, Pennsylvania (via Lake Erie), and New York. Almost all of Ontario's 2,700-kilometre border with the United States follows rivers and lakes, starting from Lake of the Woods in the west and running along the Great Lakes drainage system. Only about one kilometre of that border is actual land, made up of portages like the Height of Land Portage on the Minnesota line.

Most of Ontario's people and farmland are concentrated in Southern Ontario, where manufacturing drives the economy, though agriculture remains important. Northern Ontario, by contrast, is thinly populated, with cold winters and dense forests; its main industries are mining and forestry.

The name "Ontario" likely comes from Indigenous languages—either the Huron (Wyandot) word *Ontarí:io*, meaning "great lake," or the Iroquoian *skanadario*, meaning "beautiful water" or "sparkling water." The province has roughly 250,000 freshwater lakes. The name first appeared in 1641, referring to the land on the north shore of the eastern Great Lakes, and was officially adopted for the province at Confederation in 1867.

Geographically, the Canadian Shield—thinly populated and rich in minerals—covers more than half of Ontario, dominating the northwest and central areas. It is partly forested and dotted with lakes and rivers, but mostly unsuitable for farming. Northern Ontario splits into Northwestern and Northeastern Ontario. The far north and northeast feature the Hudson Bay Lowlands, a swampy, sparsely forested region that is virtually unpopulated. Southern Ontario divides into four sub-regions: Central Ontario (not the geographic centre), Eastern Ontario, the Golden Horseshoe, and Southwestern Ontario (parts once called Western Ontario).

Mountainous terrain is rare, but there are large uplands, especially in the Canadian Shield (which runs northwest to southeast) and above the Niagara Escarpment in the south. The highest point is Ishpatina Ridge, at 693 metres above sea level in Temagami, Northeastern Ontario. In the south, elevations over 500 metres occur near Collingwood, above the Blue Mountains in the Dundalk Highlands, and on hilltops near the Madawaska River in Renfrew County. The Carolinian forest zone covers most of southwestern Ontario. The temperate, fertile Great Lakes-Saint Lawrence Valley in the south is part of the Eastern Great Lakes lowland forests ecoregion, but much of its forest has been replaced by agriculture, industry, and urban development. Niagara Falls, a well-known feature, is part of the Niagara Escarpment. The Saint Lawrence Seaway allows navigation from the Atlantic Ocean inland as far as Thunder Bay in Northwestern Ontario. Northern Ontario accounts for about 87% of the province's land area, while Southern Ontario holds 94% of the population.

Point Pelee, a peninsula on Lake Erie near Windsor and Detroit, is the southernmost point of Canada's mainland. Pelee Island and Middle Island in Lake Erie extend slightly farther south. All lie south of 42°N—a bit farther south than the northern border of California.

Ontario's climate varies by season and location, influenced by three air sources: cold, dry Arctic air from the north (dominant in winter, especially in the far north); Pacific polar air from the western Prairies and U.S. Northern Plains; and warm, moist air from the Gulf of Mexico and Atlantic. Temperature and precipitation depend mainly on latitude, proximity to large bodies of water, and, to a lesser extent, terrain. Most of Ontario has a humid continental climate. Three main climatic regions exist. The Great Lakes greatly affect southern Ontario's climate: in fall and winter, stored heat from the lakes moderates temperatures near the shores, giving parts of Southern Ontario milder winters and a later start to winter conditions than inland areas at lower latitudes. In many places, cooler lake temperatures delay warmer spring weather. Parts of Southwestern Ontario and the Hamilton-Niagara region (roughly south of a line from Sarnia to Toronto) have a moderate humid continental climate (Köppen Dfa), similar to the inland Mid-Atlantic states and lower Great Lakes portion of the U.S. Midwest. Summers there are warm to hot and humid, winters cold. Annual precipitation ranges from 750 to 1,000 millimetres and is well distributed throughout the year.