Heat warning issued for Tuesday and Wednesday in London and area

The Middlesex-London Health Unit has issued a two-day heat warning as temperatures are expected to soar, and a London emergency department doctor says it's important to be on the lookout for heat illness. 

Environment Canada is calling for a two-day spike in temperatures, with the daytime high on Tuesday and Wednesday expected to reach 31 C. Humidex values will make it feel more like the high 30s both days, the weather agency predicted. 

"There are many ways that extreme heat can impact our health. Heat illness is a spectrum of symptoms that can range from very mild symptoms to very, very severe symptoms," said Dr. Justin Yan, an emergency room doctor at the London Health Sciences Centre. 

"With the extreme heat, oftentimes people can feel a little bit lightheaded and dizzy, can get some nausea, and they can come to the emergency department because they're feeling excessive heat and have headaches or muscle cramps," Yan said.

"It often depends a lot on the individual and the circumstances that that individual is in when they're experiencing the heat-related illnesses." 

The health unit has a series of tips to avoid heat-related illness, including getting plenty of water, avoiding spending too much time outside if possible, and never learning a child or pet in a parked car or outside in direct sunlight. 

Heath stroke happens when the body has no ability to acclimatize to the heat, said Yan. 

"Patients who come in with heatstroke into the emergency department often have extremely high body temperatures that they're not able to cool themselves off with natural mechanisms such as sweating or getting to a cool environment or intake of water or fluid," he said. 

"These individuals who have true heat stroke can really present with an organ dysfunction, confusion, liver dysfunction, kidney dysfunction or cardiac or respiratory symptoms."

More common is heat exhaustion, which presents as heavy sweating, nausea, vomiting, cramps, dizziness or headache, and the symptoms go away after dehydration or being taken to a cooler environment. 

The most important thing is to "listen to your body," Yan said. 

"If somebody is feeling any symptoms of anything that's concerning to them themselves and it's not self-resolving after moving to a cooler environment or dehydrating, then certainly they should seek medical attention," he said. 

People have been resisting coming to the ER because they're so full, he added, but it's best to come in to get assessed and get treatment. 

Construction workers, the elderly, as well as vulnerable and marginalized people such as those who live on the street and don't have access to air conditioning, are most likely to suffer severe heat-related illnesses.