Geography and climate of Toronto
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The City of Toronto covers an area of 641 km² (247 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. 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 the adjacent municipalities of Mississauga, Brampton, Vaughan, Markham, and Pickering.
The Greater Toronto Area (GTA) extends beyond the city boundaries and 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.
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[edit] 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 in the Greater Toronto have some characteristics of those found in large coastal cities, due to such factors as local topography, proximity to the Lake Ontario shoreline, urbanized land density, isolated severe weather, etc. Lake Ontario often experiences large flucuations in water temperature due to upwelling of colder water or warm surface waters creating very localized weather conditions; this is especially true in spring in early summer.
In general, mild periods do occur in most winters (temperatures reach in the 5-10 °C range (40-50°F) and sometimes higher. There are 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 outer city and suburbs) or occasionally lower with a 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 wind chill 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 elsewhere in Southern Ontario, e.g. Barrie and London. All these cities are located to the south or east of The 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 with at least 20 cm (8 in.) accumulation, usually from powerful winter storms known as "Colorado Lows", that also affect other Great Lakes cities and the northeast US, ie. Chicago, Detroit, Boston, Montreal, etc. These are accompanied by strong east or north-east winds fetching additional moisture from Lake Ontario and because they originate from the south-west they can also bear a volatile mix of snow, ice pellets, freezing rain and sometimes just rain all of which can disrupt transportation travel in the area. Average winter snowfall is 133 cm (52 in). Another less ominous type of winter snowfall is referred to locally as an "Alberta Clipper", these usually drop drier but less snow with much more even totals across a wide area before moving on. A rare exception to the cities snowfall occurred on January 13th 1999, the-then Toronto mayor called in the Canadian Armed Forces to assist with the Snowstorm of 1999 where, within twelve days, Toronto recorded 118.4 cm of snow, much of it lake effect from Lake Ontario. January 1999 became one of Toronto's snowiest January in the past 200 years, but fell short of the snowiest month overall (March 1870, with 158.5 cm).
Summer maximum temperatures typically range from 25–32 °C (77–90 °F) with moderate to high humidity. Temperatures higher than 32 °C (90 °F) occur and in exceptional cases the mercury approaches or very rarely exceeds 38 °C (100 °F). Summer heat episodes are usually broken by cooler, drier periods not experienced in places further south in 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 vehicular exhaust and transported air pollution from heavy industry in the Midwest United States and Southern Ontario. There were a record 52 days with "smog warnings" over the summer of 2005, far exceeding the previous annual record of 28 days in 2001. This is believed to part of reason the provincial governments phasing out of coal-fired power generation in the province, although there has been numeours delays for 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. 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 under a couple of hours. Numerous roadways and bridges were washed out and insurance claims from backed-up sewers and flood damage exceeded $500 million - the worst flood in Toronto in 51 years. One major thoroughfare, Finch Avenue West, was completely washed out by Black Creek creating a huge 7 m (23 foot) deep hole. Re-construction of the roadway was completed more than six months later.
Such events with greater intensity are likely to occur more often in the future because of Global Warming and increased Urbanization due to the Urban heat island. For example in the past fifteen years 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, the average minimum temperature in the last ten years (1997-2006) has risen dramatically by 1.7°C (3°C) over the same 30-year normal period albeit a much shorter period of record. The previous decade has seen remarkable stretches of above normal conditions. At the airport, from 1998 (the warmest year on record) through the end of 2006 there was only 3 months of below average temperatures out of 84 months. A previous study [1] analyzes urbanization 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 or just 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 changeable air masses.
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).
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °C | -1.1 | -0.2 | 4.6 | 11.3 | 18.5 | 23.5 | 26.4 | 25.3 | 20.7 | 13.8 | 7.4 | 1.8 | 12.7 |
| Avg low °C | -7.3 | -6.3 | -2.0 | 3.8 | 9.9 | 14.8 | 17.9 | 17.3 | 13.2 | 7.3 | 2.2 | -3.7 | 5.6 |
| Avg high °F | 30.0 | 31.6 | 40.3 | 52.3 | 65.3 | 74.3 | 79.5 | 77.5 | 69.3 | 56.8 | 45.3 | 35.2 | 54.8 |
| Avg low °F | 18.9 | 20.7 | 28.4 | 38.8 | 49.8 | 58.6 | 64.2 | 63.1 | 55.8 | 45.1 | 36.0 | 25.3 | 42.1 |
| Precipitation (cm) | 6.1 | 5.1 | 6.6 | 7.0 | 7.3 | 7.2 | 6.8 | 8.0 | 8.3 | 6.5 | 7.6 | 7.1 | 83.6 |
| Precipitation (in) | 1.9 | 1.8 | 2.3 | 2.6 | 2.6 | 2.6 | 2.8 | 3.2 | 2.8 | 2.5 | 2.6 | 2.4 | 30.1 |
| Source: Environment Canada [1] Dec 2006 | |||||||||||||
[edit] See also
[edit] References
- ^ Canadian climate normals for 1971 to 2000, Environment Canada (2004). Retrieved on 2006-12-05.
