Hot and humid weather conditions will come to an end for the Greater Toronto and Hamilton areas and eastern Ontario by Wednesday night, Environment Canada says.

According to the federal weather agency, a slightly cooler and less humid air mass will slowly move into the region on Wednesday. 

“Temperatures Wednesday night will drop to the mid to upper teens,” the federal weather agency said in an updated heat warning on Tuesday evening.

In Toronto, daytime highs on Tuesday will be about 30 to 33 C, with the humidity making it feel closer to 37 to 40. Overnight lows will be between 20 to 23 C. 

On Wednesday, the daytime high will be 29 C, but will feel closer to 37 with the humidity. The low is expected to be 18 C.

The forecast calls for a mainly cloudy Wednesday with a 40 per cent chance of showers. There is a risk of a thunderstorm late in the morning and afternoon. 

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Toronto Public Health reports 51 heat-related emergency room trips so far this month, more than in July 2024. Mayor Olivia Chow says more needs to be done to improve the city’s hot weather plan.

Environment Canada warns hot, humid air can lead to worsening air quality. The air quality health index for Toronto was at 3, or “low risk,” as of Tuesday evening.

People are advised to drink water often, watch for signs of heat exhaustion and check on those at-risk for heat illnesses, according to the federal weather agency. 

It suggests turning on air conditioning, using a fan and staying indoors to limit exposure to the heat.

“Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses,” Environment Canada said in its updated warning.

Signs of heat stroke can include red and hot skin, dizziness and nausea.

For residents looking to cool down during the heat warning, the city says Metro Hall is open around the clock as a cool space. The city says residents can cool down at more than 500 spaces across Toronto as part of its heat relief network.