Environment Canada has issued a heat advisory for southern Ontario ahead of the weekend, with humidex values expected to reach the low 40s from Friday afternoon through Sunday evening.

Toronto, Hamilton, and the Niagara region are all under the advisory. Officials are recommending the usual precautions: limit outdoor activity in the early afternoon, check on older neighbours, and never leave pets in vehicles.

Relief arrives Monday, when a cold front is forecast to drop temperatures back to seasonal norms.