The city of Toronto is under an extreme heat alert.

The medical officer of health issued the warning due to prolonged hot temperatures in the city.

A heat warning from Environment Canada also remains in effect for the GTA and much of southern Ontario, with a high of 33 C and humidex values near 40 expected in Toronto Monday.

The city’s cooling centres will be open to the public.

During an extreme heat alert, the public is reminded to stay hydrated and to check in with family, friends and neighbours, especially isolated seniors.

It’s particularly risky outside for people with chronic and pre-existing illnesses, infants and young children, people on certain medications, and those who are marginally housed or homeless.

Monday’s alert is the third of the year.