A heat warning will continue into the weekend for Niagara.
Environment Canada says hot and humid conditions are expected for the weekend, with daytime maximum temperatures reaching 29 to 31 degrees Celsius, with humidex values of 37 to 42.
Saturday's overnight low is 20 to 23 degrees Celsius.
Officials say hot and humid air can also bring deteriorating air quality and can cause the air quality health index to approach the high risk category.
Extreme heat affects everyone. the risks are greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors.