In a statement issued late Tuesday, the agency said “high levels of air pollution have developed.”
“The heat and sunshine conditions have resulted in increased ozone concentrations at ground level,” the statement said.
The agency said “high-risk” air quality index health values are expected to be maintained for one to two hours and that higher levels of pollution may remain local tonight.
The statement, which closes on the first official day of summer, applies to Toronto, York, Durham, Peel, Halton, Hamilton, Niagara and other areas.
“People may experience symptoms such as increased cough, sore throat, headaches or shortness of breath,” said Environment Canada. “Children, the elderly and those suffering from cardiovascular or lung disease, such as asthma, are at particular risk.”
The area is already under heat warning due to two days of intense heat.
Toronto broke a 10-year temperature record on Tuesday, reaching 35.3 C in Toronto Pearson, surpassing the previous record for June 21 of 34.4 C set in 2012.
Wednesday is expected to be another suffocating day, with an expected high of 31 C, although it will be closer to 39 with humidex. A UV index of 11, or “extreme”, is also expected.
People are reminded to never leave pets or people in parked vehicles, to stay hydrated and to avoid strenuous outdoor work during the hottest times of the day, if possible.
The temperature is expected to drop slightly on Thursday, although it will remain warm with an expected high of 28 degrees.
