A heat warning remains in effect for southern Ontario—including King Township—with Environment Canada warning of temperatures climbing above 30 C.
Temperatures are expected to be 29 and 30 C, with humidex values of 37 to 40.
The federal weather agency is reminding people that hot and humid air can also bring deteriorating air quality and can result in the Air Quality Health Index approaching 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," Environment Canada said.
"Watch for the effects of heat illness: swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions. Drink plenty of water even before you feel thirsty and stay in a cool place. Never leave people or pets inside a parked vehicle."
Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion.
Environment Canada says areas near the lakes could be slightly cooler than regions further inland, and temperatures will be several degrees cooler for Friday.