Geography of Ontario

Continent	North America
Region	Eastern Canada Central Canada
Coordinates	49°15′0″N84°29′59″W / 49.25000°N 84.49972°W /49.25000; -84.49972
Area
• Total	1,076,395 km2 (415,598 sq mi)
• Land	85.3%
• Water	14.7%
Coastline	3,840 km (2,390 mi)
Borders	Total land borders: U.S. statesMichigan,New York,Minnesota; Canadian provincesManitoba,Nunavut, andQuebec
Highest point	Ishpatina Ridge 693 m (2,274 ft)
Lowest point	Hudson Bay sea level
Longest river	Albany River 980 km (610 mi)
Largest lake	Lake Superior 28,700 km2 (11,100 sq mi) (Canadian portion only)

Ontario is located inEast/Central Canada. It is Canada's second largest province by land area. Its physical features vary greatly from theMixedwood Plains in the southeast to theboreal forests andtundra in the north. Ontario borders Manitoba to the west,Hudson Bay andJames Bay to the north,Quebec to the east, and theGreat Lakes and theUnited States to the south. The province is named for GreatLake Ontario, an adaptation of theIroquois wordOnitariio, meaning "beautiful lake", orKanadario, variously translated as "beautiful water". There are approximately 250,000 lakes and over 100,000 kilometres (62,000 mi) of rivers in the province.

Almost 94% of the population is concentrated withinSouthern Ontario, where the population was over 12,850,000 in the 2011 census. TheGolden Horseshoe is the most populous part of Southern Ontario, with a population of 9,765,188 in the 2021 census.^[1]

Ontario is the most populous province in Canada.Southern Ontario is one of the densest regions in the country.The north is vast and sparse compared to the south. The national capitalOttawa is located in Ontario bordering Quebec. Located within theGolden Horseshoe,Toronto is the capital of Ontario, the financial centre of Canada, and the country's most populous city.

Ontario is the second-mosturbanized province afterBritish Columbia, with 85.9% of the population living in urban areas.^[2]

Population by Statistical Area Classification^[3]

Statistical Area Classification	2011 Census		2006 Census		Change
	Population	% of total	Population	% of total
Within CMAs	10,270,006	79.9%	9,591,529	78.9%	7.1%
Within CAs	1,133,127	8.8%	1,128,614	9.3%	0.4%
Total CMA/CA	11,403,133	88.7%	10,720,143	88.2%	6.4%
Strongly influenced	644,299	5.0%	631,410	5.2%	2.0%
Moderately influenced	555,931	4.3%	554,062	4.5%	0.3%
Weakly influenced	225,197	1.8%	232,107	1.9%	3.0%
Not influenced	23,261	0.2%	22,560	0.2%	3.1%
Outside CMA/CA	1,448,688	11.3%	1,440,139	11.8%	0.6%
Total	12,851,821	100.0%	12,160,282	100.0%	5.7%

Southwestern Ontario and a narrow strip along the coast of theSaint Lawrence River are in theMixedwood Plains, a fertile and productiveecozone that is typically flat with rolling hills, and was once covered by forest before its use foragriculture, and laterurbanization, resulted indeforestation of vast swaths of the area. To its north is theBoreal Shield, the largest provincial ecozone, extending from south-central Ontario to cover most of northern Ontario, where it abuts theHudson Plains. TheNorthwestern Ontario portion of this area is part of theMidwestern Canadian Shield forests ecoregion ofboreal forest that spreads west throughManitoba andSaskatchewan. The plains that cover the heartland of Ontario are a transitional ecozone characterized by boreal features in the south andtundra landscapes in the north. This extends the entire range of the northern coast of Ontario withHudson Bay andJames Bay, at which numerouswetlands act asstaging and nesting grounds formigratory birds. The waters of the two bays are in theArctic Archipelago Marine ecozone, forming its southern, subarctic extent.

Ontario, owing to its size, has diverse geology that varies in structure, age, and lithology. About 61% of the province is covered by theCanadian Shield, mostly withPrecambrian rock.^[10] These rocks contain large mineral deposits that are vital to the economy of northern Ontario. The shield can further be divided into three sections. The northwestern parts of the Shield, located roughly north and west of Sudbury, are known as the Superior Province;^[10] this is the largest of the three sections, covering about 70% of the Shield portion in Ontario.^[11] This region is more than 2.5 billion years old and is composed offelsic intrusive rocks.^[10] In the northernmost parts of the Superior Province, the geology of the region is dominated by granite and gneiss rocks.^[11] The central region of the Shield, known as the Grenville Province and located south of Sudbury, is 1.0 to 1.6 billion years old and is dominated by sedimentary rocks showing evidence of being subjected to metamorphism.^[10] It makes up about 20% of the Canadian Shield in Ontario. These rocks were metamorphosed between 990 million years ago and 1.08 billion years ago. The third region, known as the Southern province which is a narrow region from Sault Ste. Marie to Kirkland Lake, is made of rocks dating 1.8 to 2.4 billion years ago.^[10] The Hudson Bay lowlands, located north of the Canadian Shield, are mainly made of sedimentary rocks from theSilurian Period, although some parts date from theOrdovician andDevonian periods.^[10] This area covers 25% of the province. Most of the bedrock in the Hudson Bay lowlands is composed of limestone and carbonate-dominated sedimentary rock.^[12]

The longest border is with the Canadian province ofManitoba to the west for approximately 1,025 km (637 mi) along a line defined as theNorthwesternmost point of theLake of the Woods to latitude 52°50' N then a diagonal line to the point where the shore ofHudson Bay meets the 89th meridian west of Greenwich.^[13][14] The boundary of Ontario on Hudson andJames Bay does not extend beyond the shoreline, as all islands within the bays belong toNunavut. The border withQuebec is defined by a line due north of the head ofLake Timiskaming to James Bay,^[15] and southeast from there, theOttawa River for about 620 km (390 mi). The boundary follows a small portion of land south of the Ottawa River until it meets theSaint Lawrence River nearCornwall.

Ontario also shares borders with severalU.S. states. From west to east, theMinnesota border consists of theLake of the Woods,Rainy River,Rainy Lake and its tributaries. The border then includes the only 1 km of land of its entire 2,700 km U.S. border, theHeight of Land Portage, which divides theArctic Ocean andNelson River watershed from that of theSt Lawrence River and theAtlantic Ocean. The U.S./Minnesota border then follows tributaries of thePigeon River to its mouth at Lake Superior. Ontario bordersMichigan acrossLake Superior, theSaint Mary's River,Lake Huron, theSt. Clair River,Lake St. Clair, theDetroit River, andLake Erie. The province also bordersOhio andPennsylvania across Lake Erie. The 309 km boundary withNew York includesLake Ontario, theSt. Lawrence andNiagara rivers.

An extensive amount of land along the south and west shores ofJames Bay andHudson Bay is low and covered with wetlands. The land in the North-east and North-west, generally north ofLake Superior, is theCanadian Shield where most of Ontario's highest points are found.^{[citation needed]}

Further south, many hilltops of the Algonquin, Haliburton and Madawaska Highlands, which are also part of the shield that covers much of the north, surpass altitudes of 500 m (1640').^{[citation needed]}

The Municipality of Temagami is located on the northeast arm of Lake Temagami, 100 km north of North Bay. Ontario's highest point, Ishpatina Ridge (693 metres), is within the municipality's boundaries. The next highest points are inDufferin,Grey and the western side ofSimcoe counties, where the elevation ranges from 430 m (1,400') to 540 m (1,750'). Much of the higher land sits atop theNiagara Escarpment in a generally flat area known as the Dundalk Highlands. Just to the south, inWellington County andWaterloo Region, general elevations are from 300 m (1,000') to 400 m (1,300'). A striking topographical feature of the Niagara Escarpment is its limestone cliff face, in general between 80 m (250') and 100 m (330') above the surrounding land, extending from the Niagara peninsula northwest to theBruce Peninsula.^[16]

The flattest areas of the province can be found in the lowlands of the far north, and in southwestern and eastern Ontario.^{[citation needed]}

Ontario is known for the large number of lakes and rivers it contains. About one-fifth of the world's fresh water can be found in Ontario.^[17] Ontario is also known for being the only province in Canada that touches theGreat Lakes. Ontario touches four of the Great Lakes:Huron,Lake Ontario (the province is named after the lake),Erie andSuperior.

Ontario's vast rivers and lakes originally opened the province for exploration and have made possible hydroelectric power, mills and various forms of industrialization. Most of Ontario is fed by rainfall, and in most partssnow is relied on. Precipitation is most common in the southern and central parts of Ontario where variations among the seasons are not especially great; but winter and spring are less aqueous than in northern and northwestern Ontario.^[18]

The climate of Ontario varies by season and location.^[19] It is affected by three air sources: cold, dry, arctic air from the north (dominant factor during the winter months, and for a longer part of the year in far northern Ontario); Pacific polar air crossing in from the western Canadian Prairies/USNorthern Plains; and warm, moist air from the Gulf of Mexico and the Atlantic Ocean.^[20] The effects of these major air masses on temperature and precipitation depend mainly on latitude, proximity to major bodies of water and to a small extent, terrain relief.^[20] The surrounding Great Lakes greatly influence the climatic region of southern Ontario.^[19] During the fall and winter months, heat stored from the lakes is released, moderating the climate near the shores of the lakes.^[21] This gives some parts of southern Ontario milder winters than mid-continental areas at lower latitudes.^[21] In general, most of Ontario's climate is classified ashumid continental.^[20]

Ontario has three main climatic regions:

Almost all of southern Ontario either falls in theKöppen climate classificationDfb orDfa, found inWindsor and over a large part ofSouthwestern Ontario, and further to the east, in the city ofToronto and over most of the southern half of theGolden Horseshoe wrapping around the west end of Lake Ontario, which encompasses the Niagara Region. Some cities straddle the zone boundary, such asLondon, the upper part ofHamilton, andCornwall in Southeastern Ontario. Other cities fit into theDfb schema, includingKitchener,Barrie,Kingston andOttawa. The region has warm, humid summers and cold, usually moist winters. Extreme heat and cold usually occur for short periods. It is considered a temperate climate when compared with the remainder of continental Canada. In the fall and winter, temperatures are moderated by the delayed cooling of the Great Lakes; this effect is reversed in spring and summer when afternoon warming is tempered. The lakes' moderating effects allow for a longer growing season than areas at similar latitudes in the continent's interior; some areas exceed 200 frost-free days and have an annual mean temperature of 10 °C (50 °F). Both spring and fall generally consist of mild days and cool nights but are prone to drastic temperature changes over a short timespan. Annual precipitation ranges from 75 to 110 cm (30–43 in) and is well distributed throughout the year with a usual summer peak. Upland areas in this region have cooler conditions, examples would beMount Forest andBancroft, generally more precipitation (especially snowfall), putting them firmly into theDfb climate scheme. Most of Southern Ontario lies in the lee of the Great Lakes, producing abundant snow in some areas: (London,Goderich and Barrie, for example) receive an average of over 2 m (80") annually, while some other areas are not in the direct line of snowbelt activity can receive on average less 1 m (40") of snow per year, such as inChatham andBrantford.

Also included in theDfb climate are the southern reaches of including the cities of Sudbury and North Bay, which have a more severe humid continental climate. This region has warm and humid summers but with more variability, a much shorter growing season with cold, longer winters with roughly equal annual precipitation to the south. Along the eastern shores of Lake Superior and Lake Huron (includingGeorgian Bay), the longer winters and frequent heavy lake-effect snow squalls increase seasonal snowfall totals upwards of 3 m (120 in) in some locations, such asWawa but further north inTimmins far removed from the lakes influence.

Köppen climate classificationDfc: The northernmost parts of Ontario — primarily north of 50°N and with no major cities in the area — have asubarctic climate with long, severely cold winters and short summers, with dramatic temperature changes possible in all seasons. In summer, hot weather occasionally reaches even the northernmost parts of Ontario for brief periods, although humidity is generally lower than in the south. With no major mountain ranges blocking sinking Arctic air masses, temperatures of −40 °C (−40 °F) are not uncommon. The snow stays on the ground much longer here than in other regions of Ontario; snow cover is usually present to some extent between October and May. Surprisingly warm to hot temperatures sometimes occur in Northern Ontario communities when there is a long flow of wind from the south, as happened on 10 May 2022 whenMoosonee recorded Canada's first 30 °C or 86 °F reading of the year.^[22]

Severe and non-severe thunderstorms peak in frequency from June through August but can occur at any time. Thunderstorm activity is frequent, and occasionally severe across the South, but also in Central andNorthwestern Ontario. Thunderstorms form from daytime convective heating and frontal activity; in the south, lake breeze convergences also intensify storms. Another severe type of thunderstorm is known as aMesocyclonic Convective Complex orDerecho, which is a larger cluster-type thunderstorm mass with a more or less circular shape, often with a pronounced bow shape at its front or leading edge. During periods of hot weather in summer, they often develop in the afternoon west of the Great Lakes then strike Southern and Central Ontario at night with great forward motion, bringing severe straight-line winds over wide areas resulting in damage to forests, power interruption and infrastructure damage. The areas with the highest severe weather frequency in the province are Southwestern (Windsor, Chatham, Stratford corridor) and Central Ontario (Simcoe County including the city of Barrie,Lake Simcoe and theKawartha Lakes region), both areas often getting amplified storms resulting from the Lake Breeze Front convergence. London has the most lightning strikes per year in Canada, averaging 34 days of thunderstorm activity per year. In a typical year, based on averages from the period from 1980 to 2009 compiled by the Northern Tornadoes Project,^[23] Ontario averaged 18.2 confirmedtornado touchdowns per year.^[24] There were a record 29 tornadoes conformed in both 2006 and 2009.These tornadoes, however, are only on occasion destructive (the vast majority are classified as EF0 or EF1 on the Enhanced Fujita scale). In Northern Ontario, some tornadoes go undetected by ground spotters because of the sparse population and remote landscape; they are often discovered after the fact by aircraft pilots, where aerial observations of damaged forest confirm occurrences. All of Northern Ontario north of a line fromLake Nipigon toTimmins has no weather radar coverage byEnvironment Canada making it difficult to detect tornadoes in far northern Ontario when they occur. Tropical depression remnants can cause copious rains and winds in the south, but are rarely deadly. A notable exception wasHurricane Hazel in October 1954.

• Geology of Ontario
• Geography of Canada
• Demographics of Ontario
• List of islands of Ontario
• Southern Ontario
• Ontario Peninsula
• Northern Ontario

• Geography of Ontario at www.ontario.caArchived 31 October 2012 at theWayback Machine

• Geography of Ontario

• Webarchive template wayback links
• All articles with dead external links
• Articles with dead external links from June 2023
• Articles with short description
• Short description is different from Wikidata
• Use Canadian English from January 2024
• All Wikipedia articles written in Canadian English
• Use dmy dates from January 2024
• Pages using gadget WikiMiniAtlas
• All articles with unsourced statements
• Articles with unsourced statements from December 2024