A special weather statement from Environment Canada is predicting high heat and humidity into Saturday in Barrie, Collingwood, Hillsdale, Midland, Coldwater, Orr Lake, Orillia, Lagoon City, and Washago.
According to the statement, daytime maximum temperatures on Friday will be near 30 degrees Celsius, with expected humidex values in the high 30s in the afternoon over some areas.
Overnight minimum temperatures will remain near 20 degrees Celsius between Friday and Saturday.
On Saturday, temperatures will remain in the upper 20s, with humidex levels in the mid- to upper 30s, the statement says.
However, the statement says, there will be a passage of a cold front on Saturday, and cooler temperatures and lower humidity are expected for the remainder of the weekend.
The same alert is also in effect for the Parry Sound and Muskoka areas.