Environment Canada says most of southern Ontario will continue to swelter in the heat for another day.
Meteorologist Peter Kimbell says a heat warning remains in effect from Windsor through to Ottawa, though some isolated pockets around Kingston and the northeast shore of Lake Erie are exempt.
He says a warning goes into effect if a region experiences two days in a row of daytime temperatures of at least 31 degrees Celsius and overnight lows of at least 20 degrees.
He says a cold front is supposed to start passing through in the next 24 hours, bringing cooler temperatures with it.
Kimbell says the warnings should be lifted by later in the day on Tuesday.
While the warnings are in place, Environment Canada urges those who are susceptible to the heat to drink plenty of water even before feeling thirsty and seek relief from the heat when possible. It also cautions pet owners not to leave animals in parked cars.