It will be a very hot weekend in southern Ontario. According to Environment Canada, daytime highs are expected to hit 31 to 33 degrees Celsius on both Saturday and Sunday. With the humidex, it will feel closer to 40. And there will be little to no relief on Saturday night. The agency said the temperature will only drop to 25, or perhaps as low as 21 degrees Celsius, through the overnight. The warning includes almost all of southern Ontario, from Windsor to Niagara Falls, Peterborough to Orillia, and as far west as Owen Sound. The heat event is expected to end Sunday night. Signs of heat illness Heat illness is a serious concern when the mercury rises, especially in older adults, infants, young children, pregnant people, those with physical or mental illnesses, people with mobility issues, those who work outside and the homeless community. Symptoms of heat exhaustion include: Heat stroke, meanwhile, is considered a medical emergency. Those symptoms include: If someone is experiencing heat stroke, experts advise moving them to a cool place, giving them water and placing ice packs on their body. Call 911 immediately. The Waterloo Region Association of Professional Paramedics is also warning that a graphic circulating online about heat stroke and heat exhaustion contains misleading information. Beating the heat The key to avoiding heat illness is to plan ahead. Here are a few things to keep in mind: Cooling centres The best way to get relief from the heat and humidity is to seek out a designated cooling centre. The Region of Waterloo has locations listed on their website. They include libraries, community centres, museums and regional offices. The map also includes a list of public swimming pools and splash pads. Protecting your pets Leaving pets inside a hot vehicle, even for a few minutes, may be dangerous. Dogs can experience heatstroke, which could lead to organ failure and, ultimately, death. The Humane Society of Kitchener Waterloo & Stratford Perth said once the weather starts to get warm, they receive calls daily about pets left alone in cars. “Even if there’s water in the car, even if you leave the car running with the air conditioner on, you never know when your battery might die,” explained HSKWSP Outreach Coordinator Stacy Murphy. “It’s just not worth the risk.” She suggests calling 911 first before the humane society. Signs of an overheated pet include: If your pet is suffering from the heat, it’s a good idea to gradually cool them down. Experts suggest using a cool blanket or towel that is wet. Avoid using ice. “Ice water can shock animals, so it’s important to cool them down gradually,” said Murphy. Owners should keep pets at home when the temperature climbs but if they need to go outside, keep them off the pavement as much as possible, only go for a short walk, or take them out in the morning or evening when it’s cooler. “If you can’t put your hand on the pavement and not get too hot too quickly, then your pet probably can’t be walking on the pavement in that heat,” Murphy said.