"Temperature will reach 30 degrees over southwestern Quebec in the next few days and hover around 20 degrees during the night. Although humidex values should not exceed the warning criteria, combination of high daytime and nightime temperatures could cause problems to vulnerable individuals, particularly in strongly urbanized areas," the warning reads.
Here are the weather forecast details for the next 24 hours.
Today: A mix of sun and cloud. 30 per cent chance of showers this afternoon. Wind becoming southwest 20 km/h this afternoon. High 30 C. UV index 8 or very high.
Tonight: Partly cloudy with 30 percent chance of showers this evening. Clearing late this evening. Low 20.
Monday: Mainly sunny. High 30 C.
Check the longer-term forecast here.