Environment Canada has a heat warning in effect for Sarnia-Lambton as well as Chatham-Kent and Windsor-Essex.
A hot and humid air mass is expected to remain in place through Monday.
Afternoon temperatures are expected to reach the low 30's with humidex values near 40 C.
Extreme heat affects everyone. Drink plenty of water even before you feel thirsty and stay in a cool place. Never leave people or pets inside a parked vehicle.
A smog and health advisory was also issued Sunday with high levels of air pollution expected.
Individuals may experience symptoms such as increased coughing, throat irritation, headaches or shortness of breath.