Toronto sits on the northwest shore of Lake Ontario in southern Canada, at approximately 43.65°N, 79.38°W. It has a humid continental climate (Köppen Dfa) with warm, humid summers and cold, snowy winters, but its lakeside position makes it one of the milder cities in Canada east of the Rockies: Lake Ontario keeps it warmer in winter and cooler in spring and early summer than places further inland.

Summer, from June to August, is warm and often humid, with July the warmest month — average highs around 26–27°C. Hot spells can push past 30°C, and the lake-fed humidity can send the humidex above 40°C, making brief hot periods feel oppressive. Lake breezes cool the immediate shoreline, and most of the summer rain arrives as afternoon thunderstorms, making it the wettest as well as the sunniest season.

Winter, from December to March, is cold and snowy but relatively mild by Canadian standards. January, the coldest month, averages highs around -1°C and lows near -9°C, with cold snaps occasionally driving wind-chill values toward -30°C. The lake's moderating influence also brings frequent mid-winter thaws that melt accumulated snow, so conditions swing between rain, ice, snow and the dangerous glaze of freezing rain.

Toronto receives around 830–860 mm of precipitation a year, spread fairly evenly with no dry season, though summer is marginally the wettest thanks to thunderstorms and late winter the driest. A good share of winter precipitation falls as snow, and lake-effect bands off Lake Ontario can occasionally dump sudden heavy snow on parts of the region. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Lake Ontario is the defining influence on Toronto's weather, damping temperature extremes, feeding summer humidity and generating lake-effect snow, so the immediate lakeshore can be markedly cooler on spring afternoons — hence the local phrase 'cooler by the lake'. Sitting in a transition zone between polar and tropical air masses, the city sees frequent, fast-moving weather systems and sharp day-to-day swings, especially in winter.

To follow any single measurement in Toronto more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.