We’ve just come off a two and a half week stretch of hot weather. The average temperature the last 17 days was about 10 degrees (F) above normal in the Twin Cities. For perspective, that’s more than one standard deviation (which is about 8 deg F this time of year) above normal, a statistically significant hurdle. It puts this time of year in the top 10% of our records for warmth.
This by itself is in keeping with our climate trends where early summer (late May into June) and late summer (September) are rapidly warming in recent decades. There’s a confluence of other factors together however that have not been seen in modern times, if at all that we’ll touch on here.
It started in Canada, but the oceans may be responsible
While we were still seeing colder than normal conditions in mid April, northern Canada was starting to scorch. Temperature anomalies were starting to exceed 10 to 20 degrees above normal with very little if any precipitation.
By May, we were getting in on the action too in Minnesota. The craziest heat (relative to normal) was still in west central Canada however.
Churchill, Manitoba, the ‘Polar Bear Capital’ of the world broke records as did Arviat north of it, seeing temperatures in the 70s, when their normal high is just above freezing in mid May. This resulted in what’s become an early break up of Hudson Bay sea ice, critical to polar bears for hunting seals.
By the way, you can join meteorologist Sven Sundgaard in Churchill this November to see polar bears and learn why so many polar bears gather near Churchill and how climate change is affecting them. The most recent population survey shows a 27% decline in their population in just a five year period. Our ‘learning vacation’ helps support the Churchill Northern Studies Science Centre, which sponsors subarctic research and conservation programs.
The extreme heat then expanded east into Quebec and Newfoundland. The unusually hot and dry weather, coming in early spring sparked numerous fires in western AND eastern Canada. It undoubtedly has the finger prints of climate change. Rapid attribution studies are able to determine that the Canadian heat was made two to four times more likely due to climate change.
One of the causes of all this is the result of some lingering effects of the rare ‘triple dip’ La Nina pattern and the rapidly developing El Nino, where cold waters in the eastern Pacific are ‘trapped’ as waters around it warm and have helped to create an anomalous pattern of cooler, stormier conditions in California and the southwest. It should be noted our planet’s oceans have set record high temperatures this year too.
This setup has helped to boost the upper level high pressure ridge east of it, which creates warmer and drier conditions beneath it. It’s then occasionally been ‘pinched off’ allowing a closed off, high pressure bubble or ‘heat dome’ to circulate back and forth across Canada and occasionally Minnesota.
Below: mid level average pattern for May 2023. Note the red blob in Canada: that’s an incredibly strong high pressure bubble or heat dome. The blue areas in the eastern Pacific and also western Atlantic represent cooler and stormier conditions which help to ‘prop up’ the ridge in central North America.
The resulting heat and fire season in Canada has been off the charts. Below is a chart of cumulative areas burned for this point in the season. Nothing in recent years comes even close.
Of course it’s affected air quality throughout North America as the upper level high has blown wildfire smoke into the U.S. as air flows clock-wise around it.
Below: two main fire areas are circled within the smoke plume map.
Minnesota is the beneficiary of all this too
While we’ve been clobbered back and forth by the heat dome as it moved east then west again, it’s created an usually high number of 90 degree days in the Twin Cities. Through June 6, it’s the fifth most ever number of 90s this early.
What should stand out to you also, is that 6 of the top 10 years are all in the past 36 years. That, despite making up only 24% of the recorded period since 1873. This is a very common theme I see in sifting through Minnesota temperature records. Consistently, the modern records have triple the number of heat statistics compared to what it should, yet another example of how shift in the average temperature have exponential effects on extremes.
Since 1990, the average number of 90s this early has tripled from an average of just about one 30 years ago to now three in our recent decade. (Note this chart works backwards from recent years back to 1990):
So what does the future hold?
There’s not much of a reason to believe the hot and dry weather won’t persist at least into early July. Pretty much ALL of our medium to longer range models forecast expanded dry weather and warmer than normal temperatures into early to mid July. Here’s just one such model, the European model showing precipitation anomalies (difference from normal) through July 20th. There’s a strong likelihood that drought to our south expands across at least far southern Minnesota.
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