Toronto Public Health wants people to stay cool this weekend after the city issued a heat warning Friday.
It says people can find respite from the heat in seven cooling stations across the city with temperatures expected to reach the mid-30s.
Environment Canada has issued an extreme heat alert for much of southern Ontario and says the temperatures will remain high into next week.
The weather agency says it will be the most significant heat event in the past few years.
WATCH: Meteorologist Ross Hull has more on the extreme heat and how long it will last
Metrolinx says the hot weather will impact the speed of GO Trains, as they may run more slowly to avoid damaging the tracks during the heat.
Get breaking National news
It recommends passengers plan ahead of time and to travel with water.
Comments