The calendar may say September, but today was one of the hottest days of the year in Toronto, with scorching temperatures and high humidity that threatened to break records in southern Ontario.

Toronto temperatures reached 34 C today, with humidity making it feel more like 43. The City of Toronto issued a heat alert early Tuesday morning, and public cooling centres were open for the day.

The same weather was felt in much of southern and southwestern Ontario, with temperatures also hitting 34 C in Windsor, Kitchener-Waterloo and London.

A humidex advisory was in effect for Toronto and much of southwestern Ontario. Officials advised people to drink plenty of water and get into an air-conditioned environment.

Near record temperatures

The Toronto temperature record for Sept. 10 is 34.8 C, set back in 2002.

Although heat alerts in September are uncommon for Toronto, today's weather was hardly historic — the record for the hottest September day in Toronto was set back in 1953 when temperatures hit 37 C.

Things will cool down on Wednesday, where the forecast high in Toronto is 33 C with showers and thunderstorms in the forecast. Temperatures in other southern Ontario cities will see a similar dip on Wednesday.