Parts of Southern Ontario to Feel Near 40°C on Monday as Prolonged Heat Wave Begins
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The feeling of summer will certainly be in the air across Southern Ontario throughout the upcoming week. A blast of warm, tropical air from the Gulf of Mexico will bring a multi-day heatwave with temperatures soaring well above 30°C starting Monday. Once you factor in the humidex, it could feel closer to 40°C, especially towards the middle of the week.
This all kicks off on Monday, with the heat building into the southwestern part of the region. Temperatures in Deep Southwestern Ontario, including Windsor, Leamington, Chatham, Sarnia, and London, could reach the low to mid-30s by the afternoon. With the rising humidity, it could feel closer to the upper 30s or even low 40s.
The rest of Southern Ontario will see daytime highs in the upper 20s or low 30s away from the Great Lakes shores. Again, the humidity will add to the sweltering heat, making it feel like the mid to upper 30s. This includes much of Central and Eastern Ontario along with the Golden Horseshoe region away from the lake.
Those around the shorelines of Lake Ontario, Erie, Huron, and Georgian Bay can expect slightly cooler temperatures thanks to the lakes providing a bit of a cooling effect. Locations such as Toronto, Burlington, Tobermory, Parry Sound, and Manitoulin Island could offer some relief from the heat.
Temperatures here will likely struggle to exceed 30°C, and the humidity will make it feel at most like the low 30s. It’s not a huge relief, but still notable given the near 40°C humidex expected further inland.
Even as we head into the overnight, we won’t see much of a cooldown to provide a break from the oppressive heat. Overnight temperatures are expected to bottom out in the upper teens or low 20s. However, the good news is that the humidity will mainly be a problem during the day, so expect some less stuffy temperatures after the sun goes down.
The same story is expected to play out on Tuesday and Wednesday. However, the heat is only expected to become more intense as the week progresses. Widespread temperatures, even without the humidex, could exceed 30°C almost everywhere in Southern Ontario. The humidex will make it feel like the 40s and, unlike on Monday, won’t be just contained to the Deep Southwest.
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Concerningly, the overnight lows on Tuesday and Wednesday could only get down to the mid-20s and climb back into the 30s by 10-11 AM. Those air conditioners and fans will certainly be running full blast all night long to keep up with this warmth.
It won’t be until later in the week that we finally get some fresher air just in time for the weekend. However, we are closely watching the end of the week for a potential severe thunderstorm threat. Isolated storms are possible earlier in the week, which we will be closely watching, but it appears that more widespread storm development won’t be a concern until Thursday and Friday.
During extreme heat, it is crucial to stay safe and take preventive measures to avoid heat-related illnesses. Make sure to stay hydrated by drinking plenty of water, even if you don't feel thirsty. Avoid beverages that can dehydrate you, such as alcohol and caffeinated drinks.
Try to stay indoors during the hottest parts of the day, usually between 10 AM and 4 PM. If you must be outside, wear lightweight, light-coloured, and loose-fitting clothing and apply sunscreen to protect your skin from harmful UV rays.
Additionally, never leave children or pets in a parked car, as temperatures can quickly become dangerously high. Check on elderly neighbours and family members, as they are more vulnerable to heat-related illnesses.
Utilize air conditioning if possible, or visit public places like shopping malls, libraries, or community centers to stay cool. Be aware of the signs of heat exhaustion and heat stroke, such as dizziness, nausea, headache, and confusion.
Call 911 immediately if you believe you or someone around you is experiencing heat stroke.
