Scorching temperatures are setting records this week as heat waves roll over Canada's East and West, while residents in Central Canada who are experiencing a particularly chilly summer are left longing for a few sweltering days.
The reason for the abnormal summer weather could be extreme fluctuations in the jet stream, according to weather experts.
Temperatures in Vancouver, Edmonton and Calgary are currently well above seasonal averages, soaring into the 30s.
A heat wave in Newfoundland lifted temperatures to an all-time high this week. The humidex value rose to a record-breaking 38.7 at the St. John's airport on Wednesday.
Thursday will likely be another record-breaker in Newfoundland, said CBC meteorologist Ryan Snoddon, with the temperature forecast to be close to 30 C, and a humidex near 40.
The 30-degree mark at the St. John's weather station is a rare event — it has reached that mark just nine times over the past 72 years.
In the West, hot weather has resulted in a summer record for power consumption in Alberta. Residents are being asked to voluntarily reduce their power consumption by turning off unnecessary lights and appliances.
A heat wave hit Edmonton this week as the city gears up for its annual Heritage Festival.
Meanwhile, chilly days, rain and sweaters at the beach have been the norm this July in Ontario and Quebec.
A jet stream that is riding high across the North, the West, and over the East Coast — but that is dipping far down in the interior with an Arctic chill — is the culprit for this summer's unusual patterns, according to experts.
Jet streams: Extreme and locked in place
"The jet stream, a fast band of moving air in the upper atmosphere that directs air masses, is sort of stuck in this one position," said CBC meteorologist Johanna Wagstaffe. "This is the same setup that we saw a few weeks ago — we didn't get much of a break from it — and now we are back to this blocked pattern."
The jet stream looks more like a roller coaster than a bungee cord this summer. (CBC News)
The jet stream is riding high on the coasts, all the way up to the Northwest Territories before diving down across the Great Lakes and then riding up again to Newfoundland and Labrador, like waves in the ocean with troughs and dips.
Where it rides high, it allows warm air to move in from the south. That southern air moves over land and does not spend a lot of time over the ocean, and it's cooking.
Where the jet stream is riding low, it brings a large swath of cold air from the Arctic abnormally far south.
Ontario, Quebec and the eastern parts of the Prairies are experiencing a cold low, the summer expression for what was known over the winter as a polar vortex. "It's like an unwanted house guest. It won't leave. It's stuck there and it keeps the warm American air out," said Environment Canada senior climatologist David Phillips.
It's not so much the heat that is strange this summer, nor is the stretch of chilly days at the beach, but where it's happening that is odd.
"It's not unusual to see extremes. We often see these blocking patterns and get heat waves or cold spells, but what is notable this year is that the heat wave isn't happening in Toronto or Ottawa or Montreal, which is where we normally see the rise in the jet stream," Wagstaffe said.
In addition, the jet stream has been locked into this abnormal pattern twice already this summer. "And for the places that are seeing such cold weather this summer, it is following such an extreme winter," she said.
From May to July, Toronto has had only four days see temperatures above 30 C, Phillips said. "St. John's, N.L., has had more days above 25 C than Toronto or Ottawa, where they may see a record of 20 C this July," he said.
Climate-change related?
While it's not definitive, these patterns could be linked to climate change. With a warming climate the jet stream is unquestionably affected, said University of British Columbia climate professor Simon Donner.
"It's possible that what we are going to see in the future is that jet stream is a bit slower and a bit wavier," Donner told CBC News. "Meaning air is going to drag up further north from southern regions and cold air is going to be dragged further south, and I think that's a little of what we're seeing this summer."
There is a growing number of studies on the connection between a changing climate and an amplified jet stream, featuring bands that stretch farther up and down in either direction.
"Newer studies show that in a warmer climate, you get greater amplitudes in the jet stream, which leads to more extreme weather. And not just extreme hot weather, but reversals too, as the atmosphere tries to balance itself out," Wagstaffe said.
'Don't write the obituary on summer yet'
Most long-range temperature models show more of the same for the rest of the summer leading into the fall.
The current weather patterns don't come as a major surprise, as they were predicted in Environment Canada's July-August-September forecast outlook.
The probability of warmer summer weather is higher along the Pacific and Atlantic coasts according to the agency's temperature models, while parts of south-central Canada are expected to see below-normal temperatures.
"At least for August it is looking like more of this cold pool of air that has come down from the Arctic," Wagstaffe said. "As we head into next week the jet stream will become less amplified, so we will see a less extreme version of what we're getting this week."
For those waiting for the chance to unzip the hoodie and cool off with a dip in the lake, all summer dreams are not lost.
"We might see a change in August," Phillips said. He expects the hot weather on the coasts to carry on, but the central part of the country might warm up as well.
"I wouldn't write the obituary on summer-like weather yet."
Plus, he said, there are reasons to be grateful, such as saving money on air conditioning and being comfortable without tossing and turning in the sweltering heat at night.
"People think summer is passing them by if they haven't had humid, hot hazy days where it's more like the tropics," he said. "But I think there is a silent majority that are saying, 'Wow, this is so comfortable.'"
Compared with last year when there was severe flooding rain in both Toronto and Calgary, "nature has actually kind of given us a break."
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