Geography and climate of Toronto

The City of Toronto, Canada, covers an area of 630 km² (243 square miles) and is bounded by Lake Ontario to the south, Etobicoke Creek and Highway 427 to the west, Steeles Avenue to the north, and the Rouge River to the east. In addition to Etobicoke Creek and the Rouge River, the city is intersected by two major rivers and their tributaries, the Humber River in the west end and the Don River just east of the central core; both flow southward before exiting at opposite ends of the Toronto Harbour, which is part of the longer Waterfront. The concentration and protection of ravines allows for large tracts of densely forested valleys with recreational trails within the city. 17.5% of Toronto is covered with trees,Fact|date=April 2008 a fairly high percentage within a large city in North America and there are ambitious proposals to double the coverage. The Iroquois Shoreline is the major west-east geological feature, the former shoreline of Lake Iroquois at the end of last glacial period. It merges with the current shore at the Scarborough Bluffs promenteau.

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 (GTA) 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. It is also located at the northern extent of the Carolinian forest zone.

In March 2005, the provincial government unveiled the boundaries of a greenbelt around the Greater Toronto Area, a 7,200 km² (2,780 mi²) area stretching from Niagara Falls to Peterborough. The greenbelt is designed to curb urban sprawl and to preserve valuable natural areas and farmland surrounding the city. Toronto is 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, UK.

Climate

Toronto's climate is moderated by Lake Ontario; its climate is among the mildest and least snowy in Canada east of the Rocky Mountain range. The climate has great annual and year to year variability, particularly during the winter months.

There can be significant regional variations in temperatures and even conditions found in Greater Toronto which have some less exaggerated characteristics of those found in large coastal cities, due to such factors as local topography, proximity to the Lake Ontario shoreline, urbanized land density and isolated severe weather. Lake Ontario often experiences large fluctuations in water temperature due to upwelling of colder water or warm surface waters creating very localized weather conditions; this is especially true in spring to early summer.

In general, mild periods do occur in most winters, with temperatures reaching in the 5-10 °C range (40-50°F) and sometimes higher. There are usually extended snow free periods even in mid-winter, particularly in the city core and areas adjacent to the lakeshore. The average January maximum is -1 °C (30 °F). There are usually a few bitter cold snaps where temperatures go from the average low near -10 °C to lows in the -20°C range (especially in the northern suburbs), with windchill making it feel colder than -30 °C. The coldest temperature recorded at Toronto Pearson International Airport was -31.3 °C(-24.3 °F) on January 4, 1981, and the coldest windchill recorded was -44.7 °C (-48.5 °F) on the same day.

Due to its location on the northwest shore of Lake Ontario Toronto is not so prone to heavy, wind-whipped lake effect snow squalls experienced in nearby American cities such as Rochester, Buffalo and Syracuse, NY or other places in Southern Ontario like Barrie and London. All these cities are located on the south or east shores of the Great Lakes, making them more vulnerable to the winds that cause the lake effect. Despite this, there are usually two or more heavy snowfalls each winter which deposit at least 15cm (6 in.) accumulation, usually from powerful winter storms known as "Colorado Lows", that also affect the Great Lakes, northeast US and other Canadian cities such as Montreal and Halifax. These storms produce strong east or north-east winds fetching additional moisture from Lake Ontario. They frequently come with a volatile mix of snow, ice pellets, freezing rain and ordinary rain, all of which can disrupt transportation, and in severe cases, power supply in the area. Average winter snowfall is 133.1 cm (52 in) downtown and 115.4 cm (46 in) at the airport.

In the last decade, two notable exceptions to the city's typical winter have occurred. First, on January 13th 1999 former Toronto mayor Mel Lastman called in the Canadian Armed Forces to assist with snow removal and clearing street. Within twelve days, the downtown Toronto weather station at the University of Toronto (Trinity College near Queens Park) recorded 118.4 cm of snow, much of it lake effect from Lake Ontario and a monthly record, but fell short of the snowiest month overall (March 1870, with 158.5 cm). February 2008 set a record for the month with 76.8 cm at the airport. The downtown station recorded 74.4 cm for February 2008 but that didn't break the record of 117.1 cm set in 1846. The winter of 2007-08 brought 209.7 cm of snowfall downtown and 194.0 cm at the airport, which did not break the all-time records: 206.7 cm at the airport (1938-39) and 313.7 cm downtown (1869-70).

Summer maximum temperatures typically range from 25–32 °C (77–90 °F) with moderate to high humidity. Temperatures higher than 32 °C (90 °F) are occurring with increasing frequency in recent summers and in exceptional cases it breaches 38 °C (100 °F). Summer heat episodes are usually broken by cooler, drier periods not experienced further south on the continent. But intense heat episodes pose a health risk to some as they often arrive with high humidity and dangerous levels of airborne smog. Parts of the population, particularly the elderly, are often not properly acclimatized to the heat when it arrives. Air conditioning is fairly common in modern buildings but it is not found everywhere, especially in smaller dwellings in the older sections of the city.

In recent years, air pollution is steadily increasing mostly from locally produced vehicular exhaust and transported air pollution from heavy industry in the Midwestern United States and Southern Ontario. There were a record 52 days with "smog warnings" over the summer of 2005. This is believed to part of the arguments used by the provincial governments to initiate a phasing-out of coal-fired power generation, although there have been numerous extensions on scheduled plant shutdowns.

Sunshine is abundant through summer, but severe thunderstorms are 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. [http://www.islandnet.com/~see/weather/elements/lakebreezewx.htm 1] . These storms sometimes move into the city. In August 2005 there were two such examples of these type of storms creating havoc, the first occurred on August 2, 2005 and is thought to have been a contributing factor in an Air France Airbus A340 crash landing into a ravine that afternoon. The second happened on the afternoon of August 19, 2005 in what has been described as a "once in a thousand year" event, up to 183 mm (over 7 in.) of rain fell in parts of the northern end of the city in less than two hours. Numerous roadways and bridges were washed out and insurance claims from backed-up sewers and flood damage to homes exceeded $500 million - the worst flood in Toronto in 51 years. One major thoroughfare, Finch Avenue West, was completely washed out by the raging Black Creek, creating a huge 7 m (23 foot) deep hole severing the road. Re-construction the pavement to grade required six months.

Such events with greater intensity are likely to occur more often in the future because of global warming and the urban heat island effect. For example, between 1992-2007 the average annual temperature has increased 0.85 °C (1.5 °F) at Pearson Airport when compared to the thirty-year normals from 1971-2000, much of this increase is occurring at night where the average minimum temperature in the last ten years (1998-2007) has risen dramatically by 1.9°C (3.3°F) over the same 30-year normal period. Interestingly, at the downtown station from February through May temperature averages have decreased slightly, whereas the September average temperature is up 2.2 °C (4 °F), indicating a recent marked increase in the seasonal lag effect combined with a possible shift in weather patterns affecting the area at different times of the year.

A previous study [http://www.cleanairpartnership.org/cooltoronto/pdf/finalpaper_gough.pdf] analyzes the heat island effect comparing data from selected regional stations, including both Downtown Toronto and Pearson Airport.

Springs and autumns feature varied weather with alternating periods of dry, sunny weather and rain. These seasons are brief when compared to summer or winter seasons. Nights are generally cool, but frosts are rare in the city. Snow can fall in early spring or late fall but usually melts quickly after contact with the ground. At these times of year, great temperature contrasts (up to 30 °C) can occur within a short time frame due to rapidly changing air masses that sweep across the continent.

The highest temperatures in Toronto at the city weather station was 41 °C (105 °F) recorded on 3 consecutive days from July 7-July 9, 1936. The coldest -33 °C (-25 °F) was recorded on January 10, 1859. Annual average precipitation is 83.4 cm (32.8 in).

tatistics

ee also

*Toronto ravine system

References

External links