With the heat alert, residents are encouraged to check up on family, friends and neighbours, especially those who are at greater risk of suffering from heat-related illness.
Residents can also beat the heat by visiting an air conditioned public place, such as shopping malls, libraries and community centres.
The heat alert comes as many outdoor Pan Am Games events are taking place across the Golden Horseshoe region. Environment Canada has also issued a heat warning for Toronto and much of southern Ontario.
The weather agency's forecast calls for a high of 30 C on Saturday and 32 C on Sunday. However, with humidity, it could feel as hot as 40 C during the afternoon hours this weekend.
It might be slightly cooler near the shorelines of the Great Lakes.
The region could see some relief on Monday, as Environment Canada calls for a high in the upper 20s.
Residents are advised to drink plenty of liquids, especially water, before they feel thirsty to decrease the risk of dehydration.
Also, they're reminding drivers not to leave pets inside a parked vehicle or in direct sunlight.
While extreme heat can put everyone at risk from heat illnesses, Environment Canada says health risks are greatest for the following people:- Older adults.
- Infants and young children.
- People with chronic illnesses such as breathing difficulties, heart conditions or psychiatric illnesses.
- People who work in the heat.
- People who exercise in the heat.
- People without access to air conditioning.
- Homeless people.