Geography of Toronto


The geography of Toronto, Ontario, covers an area of and is bounded by Lake Ontario to the south; Etobicoke Creek, Eglinton Avenue, and Highway 427 to the west; Steeles Avenue to the north; and the Rouge River and the Scarborough–Pickering Townline to the east. In addition to Etobicoke Creek and the Rouge River, the city is trisected by two minor rivers and their tributaries, the Humber River in the west end and the Don River east of downtown. Both flow southward to Lake Ontario at Humber Bay and Toronto Harbour respectively, which are part of the longer Waterfront, as well as Etobicoke Creek and the Rouge River.
The concentration and protection of Toronto's ravines allows for large tracts of densely forested valleys with recreational trails within the city. Approximately 26–28% of Toronto is covered with over 10 million trees, a fairly high percentage within a large city in North America and there are ambitious proposals to double the coverage. Toronto is on the northern edge of the Carolinian forest.
The shoreline of the former Lake Iroquois is a major west−east geological feature, which was formed at the end of the Last Glacial Period. In the west end, Davenport Road follows the ancient shoreline with the steps to Casa Loma rising above and downtown skyscrapers clearly visible to the southeast. It merges with the current Lake Ontario shoreline at the Scarborough Bluffs promontory.
The Toronto Islands are the only group of islands located on the western shores of Lake Ontario and were formed from the erosion of the Scarborough Bluffs. The Toronto Islands were originally a sand spit until a major storm separated them from the mainland during the 19th century.
Toronto's immediate neighbours are Mississauga and Brampton within the Regional Municipality of Peel, Vaughan and Markham within the Regional Municipality of York, and Pickering within the Regional Municipality of Durham. The Greater Toronto Area includes the regional municipalities of Halton, Peel, York and Durham.
The GTA is part of a larger, natural ecosystem known as the Greater Toronto Bioregion. This ecosystem is bounded by Lake Ontario, the Niagara Escarpment, and the Oak Ridges Moraine, and includes many watersheds that drain into Lake Ontario. Some parts of Toronto, such as High Park and the lower Humber River, are located in the northernmost parts of the Carolinian forest zone found in North America.
In March 2005, the Government of Ontario unveiled the boundaries of a greenbelt around the Greater Toronto Area, a area stretching from Niagara Falls to Peterborough. The green belt is designed to curb urban sprawl and to preserve valuable natural areas and farmland surrounding the city. However, some types of development including detached single residential, quarries and commercial facilities continue to get approved, exerting pressure and population growth on the Greenbelt. Toronto is among the latest in a line of cities that have implemented growth boundaries of some kind as a method of restricting urban growth, including Ottawa; Portland, Oregon; Frankfurt; Melbourne; Seoul and London.

Climate

Toronto's continental climate is moderated by Lake Ontario; its climate is among the mildest in Canada east of the Rocky Mountains, given Toronto's southerly latitude within the country. Downtown Toronto sits in a pocket of the humid continental climate zone found at the southwestern end of Lake Ontario covering the southern part of the city — including downtown, where the annual average temperature exceeds. Some of Toronto, outside of the pre-1998 city limits and some suburban areas, fall within the Dfb climate regimen. This difference partly results from the urban heat island effect. Toronto is located in hardiness zone 7a, with increasing hardiness further away from the downtown core. There is a high degree of variability from year to year and sometimes over a period of days, particularly during the winter months.
Lake Ontario's water temperature varies due to upwelling of colder water or warmer pools of surface water creating very localized thermal contrast; the deeper waters of the lake, far from the shore, remain at a near-constant water temperature of, the effect of which is either cooling or warming. This creates generally warmer nights through the colder season than would otherwise occur. When offshore winds blow in summer, they warm as they near the lakeshore in the evening; conversely, the cooling effect by the lake is most pronounced on spring afternoons, which can affect Toronto even more than other cities on the Great Lakes due its exposure to onshore winds from the east to south-east, on some days, the temperatures can be as much as 10 °C cooler than areas far removed from Lake Ontario, an effect that wanes by summer when the dominant windflow becomes more southwesterly and the lake surface temperature warms.
Springs and autumns are shorter seasons than summers and winters, and they feature varied weather with alternating periods of dry, sunny weather and rain. Many days in these seasons are sunny with pleasant rather than warm or cold temperatures. Nights are generally cool, but frosts are rare. Snow can fall in early spring or late fall but usually melt quickly after contact with the ground. At these changeable times of the year, temperature contrasts can occur within a short time frames due to rapidly changing air masses that sweep across the continent, often accompanied by high winds. Due to these airmass changes, temperatures of or above have been recorded as early as April 16 and as late as October 8. Conversely, temperatures of or below at night have been recorded as early as November 6 and as late as April 18. Snowfall has been reported as early as October 1 and as late as May 16. Toronto's weather is affected by the relative position of the polar jet stream and continental storm track, both of which pass over or near to the area with some frequency. This is determined by a number of complex global weather drivers, such as ENSO, NOA/AO Oscillations and the Polar vortex.
There is no "dry season" precipitation falls in all months with regularity, but summer rains result mostly from Thunderstorms which make for higher average amounts as a general rule with occasional dry periods. February and March rank as the driest months on average. Annual average precipitation is.

Winter and snowfall

Despite being cold, extended snow free periods occur in most winter seasons and precipitation can fall as rain with temperatures sometimes climbing above. Average winter snowfall is at the weather station in Downtown Toronto and at Toronto Pearson International Airport.
The average January maximum/minimum is / in the city. There are usually a few colder periods where temperatures remain below and less frequently below at night, with wind chills making it feel like.
Due to its position on the northwest shore of Lake Ontario, Toronto is not a direct target of heavy, wind−whipped lake-effect snow squalls that hit other Great Lake cities on the south/east shorelines of the lakes, in areas where prevailing winds amplify lake effect. Despite this, there are usually two or more heavy snowfalls each winter which deposit at least accumulation, usually from powerful winter storms known as Alberta clippers, "Colorado Lows" or panhandle hooks that pick up moisture en route to the Great Lakes. These storms can produce strong easterly driven winds that fetch additional moisture from Lake Ontario. They frequently come with a volatile mix of snow, ice pellets, freezing rain and sometimes just ordinary rain, all of which can disrupt transportation, and in severe cases, interrupt power supply. A sustained freezing rain event occurred on December 22, 2013 plunging 30% of the city into darkness, some until after Christmas Day.
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Such storms can also produce large snowfall amounts, higher totals found in areas closer to Lake Ontario, sometimes falling over a series of days or weeks creating havoc. On January 13, 1999, after a series of snowstorms, then-Toronto mayor Mel Lastman called in the Canadian Armed Forces to assist with snow removal and clearing streets. Within twelve days, the downtown Toronto weather station at the University of Toronto recorded an average season's worth of of snow, much of it lake effect from Lake Ontario and a monthly record for January, but fell short of the snowiest month overall March 1870, with, of which fell over a 5-day span. February 2008 set a record a snowfall record for the month with falling at the airport. The winter of 2007–08 brought accumulated seasonal snowfall totals of downtown and at the airport. The heavy winter snows, in combination with record rains during June–July of that year made 2008 the wettest year on the climate record with over of total precipitation. The largest single snowstorm on record took place on December 11–12, 1944, when accumulated, with on December 11 alone.
On the opposite extreme, the winter of 2011–12 had the lowest seasonal snowfall total with only. March 2012 was the warmest March on record. The least snowfall in a calendar year was 2006, with only. The El Niño influenced winter of 2009–10 had, March 2010 recorded no measurable snow, the first such occurrence in any March since 1946, and was followed by the warmest April ever on record.
Winter weather conditions in Toronto can vary greatly from one year to another and is significantly affected by global weather patterns such as El Niño–Southern Oscillation. El Niño winters are generally mild and dry, with decreased snowfall, while La Niña winters tend have more precipitation. ENSO Neutral years are more unpredictable.

Summer

Maximum temperatures typically range from with moderate to high humidity, proximity to Lake Ontario and the other lakes contribute to summer humidity but far away sources like the Gulf of Mexico also factor in. The subtropical jet can move well north of the area in the midsummer influenced largely by the strength and position of the Bermuda-Azores High and ridging over the North American continent. The cooling influence of the lake exists but can be very localized to the immediate shoreline or move further inland, but this depends on windspeed and airmass. Temperatures over occur about 7 days each year but usually lasts no longer than a couple of days at a time. However, coupled with high humidity the humidex value can rise well into the 40s during these heat events, creating great discomfort. Nighttime temperatures generally hover close to in the city but during hotter spells remain closer to. Summer heat episodes are usually broken by cooler, drier periods if only for brief periods.
Thunderstorms are also a regular occurrence and can pop up quickly, especially west and north of the city in areas more prone to the "lake breeze front" or "lake breeze thunderstorms" phenomenon, in which intense, sharply defined squall lines develop quickly on summer afternoons amplified by localized wind patterns between the Great Lakes. These storms sometimes, but not always move into the city causing localized flooding resulting from downpours with high rainfall amounts, intense lightning but less often severe winds knocking down trees and powerlines.

Severe weather and records

In addition to snowstorms, ice storms, windstorms, heavy rainfall events associated with tropical storms or very severe thunderstorms, tornadoes are rare but do occur, particularly in the northern and western suburbs. That area sits in a "tornado alley" where tornadoes occur the most often in Canada. Downtown Toronto, on the other hand, is generally shielded from tornadic storms by the lake shadow resulting from the lake breezes. Tornado warnings have been posted for the city on a few occasions in the early 21st century, however, no touchdowns have been confirmed in the city limits since a weak tornado hit Scarborough in 1998. A pair of dangerous F2 tornados did touchdown in neighbouring Vaughan during a tornado outbreak on August 20, 2009.
Toronto is susceptible to flash flooding due to its various ravines and valleys that can easily flood, as well as generally poor drainage due to its large urban area. Flooding can result from remnants of tropical storms, heavy rainfall combined with snowmelt, or summertime thunderstorms stalled out along lake breeze boundaries. Low-lying areas, such as the lower reaches of the Don River valley, are the most likely to flood. This often leads to the shutdown of the Don Valley Parkway.
was left submerged after the Humber River overflowed its banks during Hurricane Hazel in 1954.|alt=A generally flat area is completely submerged by water; trees are scattered throughout.
The tropical storm remnant of Hurricane Hazel caused 81 deaths in October 1954 due to flooding that swept homes along river banks into Lake Ontario. A sudden downburst during a strong thunderstorm was believed to have played a contributing factor in the Air France Flight 358 crash on August 2, 2005. Just a few weeks later on August 19, part of a tornado outbreak in Southern Ontario, record-breaking intense rainfall, the worst since Hazel, deluged north-central sections of the city within a couple of hours and destroying a section of a major arterial road in North York resulting in record insurance claims. Some rain gauges recorded 175 mm of rain, over 100 mm in just one hour. Another large rainstorm with intense, record rainfall amounts struck a wide swath of the city during the afternoon rush hour on July 8, 2013 flooding city streets, subway tunnels, basements and knocking out power for over two million residents, stranding commuters, some having to be rescued from a submerged train. A daily rainfall record of 126.4 mm was set at Pearson Airport, most falling in an hour and a half. Flood insurance claims are likely to exceed the 2005 storm due to a wider area affected. In the springs of 2017 and 2019, heavy rain combined with snowmelt led to the water levels of Lake Ontario to rise to record levels, flooding parts of the Toronto Islands and closing it to the public.
The most severe heat wave in Toronto occurred in 1936, during the 1936 North American heat wave, when downtown temperatures in Toronto exceeded on three consecutive days, with nighttime temperatures not falling below. The city was ill-equipped at that time to handle such a prolonged extreme heat wave, and heat stroke claimed 225 lives in the city, not counting indirect deaths from causes such as drowning. The hottest month recorded, however, was July 1921, when the average maximum temperature downtown was, and a mean temperature of still holds as the warmest month. At the airport, the highest monthly maximum average was in July 1955, records there only began in 1937. The highest humidex reached at the airport during the heat wave of July 1995, downtown on July 21, 2011.
The coldest minimum temperature of was recorded on January 10, 1859. The coldest temperature recorded at Toronto Pearson International Airport was on January 4, 1981, and the coldest windchill recorded was on the same day. The coldest month overall was at the airport in February 2015 and at downtown in February 1875. Other notable cold waves occurred in January 1994 and February 1934. Winter cold snaps pose a danger as they often come with high winds, leaving the city's homeless population very prone to frostbite and hypothermia.

Upward temperature trend

Based on public records provided by Environment Canada, the average annual temperature has increased at Pearson Airport over a period of 25 years. If compared with the thirty-year normals from 1971 to 2000, more of this increase occurred at night: the average minimum temperature has been higher. Average precipitation during the same period was close to the average of the previous period, snowfall totals down only marginally with slightly higher rainfall. September and January have seen the highest average temperature increases. Part of this warming is likely attributed to increased urban growth surrounding the airport.
An older study conducted in the 1990s analysed the heat island effect comparing data from selected regional stations, including both Downtown Toronto and Pearson Airport, enough for Downtown and the old City of Toronto to have a different Köppen climate classification from its surrounding area.

Statistics

Topography

Toronto has numerous hills and valleys that were carved out during the last Ice Age; The ravines are largely undeveloped, primarily as the result of Hurricane Hazel in 1954.
Both Dufferin Street and Caledonia Road between Davenport Road and Eglinton Avenue run across numerous steep hills and valleys. This area has often been compared with the hills of San Francisco.
Vaughan Road runs parallel to the buried Castle Frank Brook.
The Don River is categorized as an underfit river, given that the river is too small for its much wider and deeper valley. The same is true for the Humber River, the Rouge River, and the various smaller waterways of Toronto.
Grenadier Pond in High Park is the largest body of water fully within Toronto's city limits. During the winter, it becomes a natural skating rink.