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 many deep ravines allows for large tracts of densely forested valleys with recreational trails within the city. Approximately 26 to 28 percent of Toronto is covered with over ten million trees, a fairly high percentage within a large city in North America and there are ambitious proposals to double the coverage. Some parts of Toronto, such as High Park, Swansea and the lower Humber River, are located in the northernmost reaches of the Carolinian forest zone found in North America.
The shoreline of the former Lake Iroquois is a major east−west 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 natural 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 late 1850s. Artificial islands include Ookwemin Minising and the islands that constitute Ontario Place.
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.
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; Montreal; Lexington, Kentucky; Nashville and Knoxville, Tennessee; Minneapolis, Seattle, Greater Vancouver, Miami, 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 (Köppen: Dfa) zone found at the southwestern end of Lake Ontario covering the southern part of the city — including downtown (but excluding the Toronto Islands), where the annual average temperature exceeds . Toronto is located in hardiness zone 7a, with decreasing hardiness further away from the downtown core (5b in the suburbs). There is a high degree of variability from year to year and sometimes over a period of days, particularly during the winter months. Though not native to North America, cherry blossom (sakura) trees bloom in Toronto during late April and early May.
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 (in winter). 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 southeast, on some days, the temperatures can be as much as 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 (up to in extreme cases) can occur within 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 28. 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 El Niño–Southern Oscillation (ENSO), North Atlantic oscillation (NOA) / Arctic oscillation (AO) and the polar vortex.
There is no "dry season" as precipitation falls in all months with regularity (but mainly snow during the winter), 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. According to Environment and Climate Change Canada, from 1991 to 2020, 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 between in the city. There are usually a few colder periods where temperatures remain below and less frequently below at night (especially in the northern suburbs), 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 "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. Alberta clippers are less impactful, usually crossing the area quickly, bringing widespread but lighter snowfall. A sustained freezing rain event occurred on December 22, 2013, plunging 30 percent of the city into darkness, some until after Christmas Day.
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 (Trinity College near Queen's Park) 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 five days. February 2008 set a record a snowfall record for the month with falling at the airport, until broken by February 2025 with . 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, until broken by 2024 with . The largest single 24-hour and daily snowfall records occurred on December 11–12, 1944, when accumulated, with on December 11 alone. More recently on January 16–17, 2022, a blizzard dropped up to (in sections of Scarborough) of accumulated snow in the city, crippling public transportation, with most of it falling on the morning of January 17. The official storm total at Pearson Airport was This record was broken during the January 2026 winter storm.
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 strong El Niño influenced winter of 2009–10 had a low total of , 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.Ontario Weather Review
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 (ENSO). El Niño winters on the weak to moderate side are generally colder or below average in terms of temperatures (such as the winters of 1976–77, 1977–78, 1991–92, 2002–03, 2004–05, early 2007, and 2014–15) with stronger ones being much milder and soggier than normal, with more rainfall and less snowfall than average (such as the winters of 1982–83, 1997–98, December 2006-mid January 2007, 2009–10, 2015–16 and 2023–24 – second warmest winter), while La Niña winters tend have more precipitation, with more snowfall (the aforementioned 1999, 2000–01, 2008, 2009, 2010–11, 2017–18, 2022, 2024–25, and 2025–26 were La Niña winters), but tend toward above average in terms of temperatures (such as the winters of 2005–06, 2011–12 – warmest winter, 2016-17 and 2022-23). ENSO Neutral years are more unpredictable, such as the much below average winters of 1993-94 and 2013–14, the coldest, longest winter in recent memory.
Summer
Maximum temperatures typically range from with moderate to high humidity, proximity to Lake Ontario and the other lakes contribute to summer humidity but faraway 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, in some summers, it is a dominating influence.