According to U.S. National Oceanic and Atmospheric Administration(NOAA) , world’s average annual temperature is one degree Celsius warmer than it was a century ago. The 10 warmest years on record have all occurred since 2005, and seven of the 10 have occurred just since 2014 .

Canada is widely known for its brutal winter and snows, and prior to the weekend the historical high in Canada was 45°C, set in Saskatchewan in 1937, according to Environment and Climate Change Canada.

The heat over western parts of Canada and the US has been caused by a dome of static high-pressure hot air stretching from California to the Arctic territories. Temperatures have been easing in coastal areas but there is not much respite for inland regions.  

The scorching heat stretching from the US state of Oregon to Canada’s Arctic territories has been blamed on a high-pressure ridge trapping warm air in the region.

The heatwave in the Pacific Northwest, which is more accustomed to long bouts of rain than sun, resulted from a high pressure system that wasn’t moving, said Greg Flato, a senior research scientist with Environment and Climate Change Canada based in Victoria.

Weather-wise, the current heat wave in the west is due to a “heat dome,”. It’s a large area of high pressure that extends well up into the atmosphere. So in British Columbia , even at the top of the Rocky Mountains, the temperature is some 15 to 20 degrees above normal .So, when you have this dome, this high-pressure system, it’s a lot of sinking air underneath that just warms more as it comes down towards the coast.  

On top of this, the sun is shining day after day, and creating a bubble where the jet stream can do nothing but go around it . This stops the rain from coming in or cold fronts from cooling things down. Although heat domes are nothing new, while the frequency and duration in which they are happening could be attributed to climate change.

Heat waves begin when high pressure in the atmosphere moves in and pushes warm air toward the ground. That air warms up further as it is compressed, and we begin to feel a lot hotter.

The high-pressure system pressing down on the ground expands vertically, forcing other weather systems to change course. It even minimizes wind and cloud cover, making the air more stifling. This is also why a heat wave parks itself over an area for several days or longer. 

As the ground warms, it loses moisture, which makes it easier to heat even more. In the drought-ridden West, there is plenty of heat for the high-pressure system to trap.

As that trapped heat continues to warm, the system acts like a lid on a pot ,  earning the name “heat dome.” In the Pacific Northwest, the heat and the drought are working in concert, exacerbating the problem and causing temperature records to fall day after day.

The heat has resulted from a wide and deep mass of high-pressure air that, because of a wavy jet stream, parked itself over much of the region. Such an enormous high-pressure zone acts like a lid on a pot, trapping heat so that it accumulates. And with the West suffering through drought, there’s been plenty of heat to trap. This happens when strong, high-pressure atmospheric conditions combine with influences from La Nina , creating vast areas of sweltering heat that gets trapped under the high-pressure “dome.” 

In Seattle, Portland and other areas west of the Cascades, hot air blowing from the east was further warmed as it descended the mountains, raising temperatures even more.

Climate is naturally variable, so periods of high heat are to be expected. But in this episode scientists see the fingerprints of climate change, brought on by human-caused emissions of carbon dioxide and other greenhouse gases.

A strong change (or gradient) in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter triggers the heat dome .  

The western Pacific’s temperatures have risen over the past few decades as compared to the eastern Pacific, creating a strong temperature gradient, or pressure differences that drive wind, across the entire ocean in winter. In a process known as convection, the gradient causes more warm air, heated by the ocean surface, to rise over the western Pacific, and decreases convection over the central and eastern Pacific .

As prevailing winds move the hot air east, the northern shifts of the jet stream trap the air and move it toward land, where it sinks, resulting in heat waves.

The extreme heat wave seen in British Columbia is not just tied to that region. It’s still been very hot and humid in Ontario, Quebec and Atlantic Canada 

The heatwave has scorched crops across the Prairies, where farmers grow much of the world’s wheat and canola, driven up natural gas prices in the fourth-largest global producer, and increased the risks of wildfires. 

A flood warning is now effect for the Chilcotin region in British Columbia’s interior due to an unprecedented amount of snowmelt triggered by extremely hot temperatures.