The big news that everyone’s been talking about is the major heat wave that formed this past weekend over western North America and brought record-breaking heat even to such unlikely places such as the temperate rainforest of the Pacific Northwest.

It’s only the end of June, yet we’ve had air temperatures in the high 30’s—unusual for this time of year and unusual in general. What’s worse is that the nighttime minimum temperatures dropped only to values similar to the normal highs for this time of year—on Sunday it was 25⁰C overnight, hardly enough to cool the house off before Monday morning and the associated rise in temperature. By 10am on Monday it was already 30⁰C, 35⁰C by noon, with a predicted high of 40⁰C in the late afternoon.

That’s just the air temperature, not the “feels like” temperature when you factor in the humidity (the humidex). As I write this, it’s 35⁰C but feels like 39⁰C because of the humidex, which means when we hit our projected 40⁰C high it could feel like 44⁰C.

And that’s out here on the Coast. Interior regions aren’t faring much better, with temperatures in the mid 40’s. Kamloops is expected to reach 46⁰C on Tuesday. And again, that’s without the humidex. Air temperature records are falling: places like Lytton broke the record for the hottest temperature ever in Canada with 46.6⁰C on Sunday and 47.9⁰C on Monday.

But while these numbers are eye-popping (and energy-draining), what’s causing them?

An intense high pressure dome has formed over western North America, with the jet stream creating an omega-shaped arc and with air pushing down from the upper atmosphere and warming as it falls towards the land surface. The dome is high enough that the air has to fall a significant distance to reach the ground, which gives it a lot of time to warm along the way. This type of weather formation often stalls in one location, and is also known as a blocking pattern.

How a heat dome forms (via CBC).

It has led to popular attractions like The Butchart Gardens closing from Sunday to Wednesday because of the extreme heat. The University of Victoria closed on Monday. The heat also led to the suspension of Portland, Oregon cable car service, because the heat was melting their power cables. Heat has been blamed for roads buckling in Washington State, and the US Track and Field Trials in Eugene, Oregon were halted on Sunday because of the extreme heat. The heat is also rapidly melting the mountain snowpack, leading to flood evacuations in communities like Pemberton, near Whistler, BC, with low-lying areas along the Lillooet River, and in the headwaters of the Fraser River, near Mt. Robson and McBride. Other communities are running out of water, like the District of North Saanich which asked residents to conserve water because supplies were low.

The dome is expected to stay in place at least for the first few days of this week, with temperatures dropping to 28⁰C by Wednesday.

We are lucky that we have air conditioning, but that just means we’re increasing our draw on the energy grid at a time when everyone is doing the same (see this link from Alberta re: energy use), leading to record-breaking electricity demand. In tandem with the high temperatures, the wildfire danger has jumped from high to extreme on southern Vancouver Island, and is high to extreme for most of the province.

This heat wave is a wake up call about climate change, which is predicted to bring more extreme heat and higher low temperatures as the average temperatures increase. There’s a great graphic in this Washington Post article that shows how this works.

This has serious implications for regions like ours that aren’t used to such high temperatures. We will have to adapt our infrastructure and our activities to higher temperatures, something that is often overlooked in climate change planning. We will also have to manage our power and water usage, both resources which are strained during a heat wave.

And while the heat wave will recede and become just a memory, there is a high likelihood that something similar could happen again. As I wrote last week about shifting baseline syndrome, this type of weather event could become the norm rather than an anomaly, and we may forget that at one time it was a rare occurrence.

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