Millions of Canadians in path of 'incredibly serious' heat dome

Hour by hour, the heat is settling in over much of eastern Canada and will become more oppressive as the sunniest days of the year approach. In Toronto, where urban infrastructure only makes it worse, the district school board is telling parents to dress their kids in light clothing and have them drink lots of water. Natalia Blasovic bikes most days and knows from experience she has to cut back. The heat can get to you. I I've already fallen before. Phil Monahan is a runner. I've got to take a break from running for a week. I feel like every year it's getting sort of where the summer is expanding further and further into May on the one end in October and the other end and in between, the heat grows more intense. In this era of climate change, this is more than a heat wave, where the jet stream can move warm air into a region and out again. A heat Dome starts with a Ridge of high pressure in the atmosphere that lingers. The pressure causes the air to sink, the compression creating more heat and that prevents the updraft that can produce clouds and rain. That brings more relief and instead you get unrelenting sun and heat. British Columbia experienced a devastating heat Dome 3 summers ago, the hottest temperatures in Canadian history and the deadliest extreme weather event. More than 600 heat related deaths. This is incredibly serious and this is something that's really important to pay attention to because heat domes really highlight that this is heat that is above body temperature that makes it very difficult for your body to cool. Doctor De Ramsey says the homeless who cannot escape the heat are at great risk, along with children and the elderly. We know that they are disproportionately affected by heat and are so vulnerable to these changes in our environment. Many do understand this is one week to be out of the sun and the heat from 12:00 to 5:00. We are always at home. We are air conditioning very we drink more water, we're stay hydrated. I don't like to go out when there's like the I would feel it's kind of hot. So it make me feel uncomfortable. Natalia headed home early on Monday. Doctors say the ability to keep cool can be overwhelmed with the temperatures and humidex levels that are expected this week. Eric Sorenson, Global News, Toronto.