Temperatures in the region will crack 30 degrees today.
But any Environment Canada warnings are concentrated in areas of southwestern Ontario including Sarnia-Lambton and east through London to the Waterloo Region and Guelph.
However, the temperature across Huron, Perth, Bruce, Grey and Wellington are expected to be 30 or higher. And humidex values are expected to be high.
The heat can also affect air quality.
The hot weather is expected to stay through tomorrow with a cold front expected tomorrow night. That will knock down the temperature to the low 20's and bring some rain.