Environment Canada (EC) has issued a heat warning for Sarnia-Lambton, Chatham-Kent, and Windsor-Essex.
The national weather agency said it's the first significant heat wave of the season with dangerously hot conditions beginning on Saturday afternoon and expected to continue through much of next week.
Daytime highs are forecast to be between 31 and 36 degrees Celsius, with humidex values of 40 to 45 C.
Overnight lows of 21 to 25 C will provide little relief from the heat.
We're being urged to take action to protect against heat exhaustion and heat stroke.
Signs may include headache, nausea, dizziness, thirst, dark urine, and intense fatigue.
If you feel any of these symptoms, stop your activity and drink water.
In severe cases, move to a cool place, remove extra clothing, and apply cold water or ice packs around the body.
Plan and schedule outdoor activities during the coolest parts of the day.
Limit direct exposure to the sun and heat, wear lightweight, light-coloured, loose-fitting clothing and a wide-brimmed hat.
We're encouraged to check on vulnerable populations, including the elderly and never leave pets inside of a hot vehicle.
Call 9-1-1 or your emergency health provider if you, or someone around you, is showing signs of heat stroke.