Environment Canada has issued a heat warning for Chatham-Kent, Rondeau Park, Windsor-Essex and Leamington.
Humidex values are expected to peak at 40 C (104 F) Friday afternoon.
Daytime temperatures are expected to peak in the low 30s Celsius or high 80s, low 90s Fahrenheit. Nighttime, the temperature will be in the low 20s C or 70s F.
The agency says showers Saturday and Sunday should provide some relief and cooler weather is expected on Monday.
The Windsor-Essex County Health Unit has also issued a warning for Windsor-Essex.
Tips to cope with extreme heat include drinking plenty of water and staying in an air-conditioned building.
Residents are also reminded to check in with elderly neighbours and those with chronic conditions, as well as never leave pets or children in a parked vehicle.
