Dumb question but are heat waves like this caused by global warming or are they the result of local weather systems that just happen to line up in a way that results in especially high temps?
Global warming is a climate change. Single weather events like a heat wave may very well be the result of global warming, but it could also be a random event.
One good example are floods. We usually talk about 5-year, 20-year and 100-year floods. A 100-year flood could be triggered by unusually large snowfall during the winter followed by a particularly wet spring with a sudden heat wave that melts all the snow in mountains at the same time.
https://en.wikipedia.org/wiki/Global_temperature_record
First actual recording of temperature in Seattle, Washington dates to 16 February 1870.
https://mrcc.illinois.edu/FORTS/histories/WA_Seattle_Conner....
I am not readily finding a similar document for Portland, Oregon.
In the US, we sometimes have oral histories from Indigenous populations that help clue us. In Southern California, there were Native stories about their ancestors being aware of a lake in what is now the Salton Sea and was dry land when White settlers or explorers were first going into that area.
We have data models. We have oral histories. We think we know what the weather was like for thousands of years but actual recorded weather goes back less than two hundred years.
So the reality is that we know for certain less than our stories in popular media might lead you to believe. Please keep in mind that our awareness of a hole in the ozone was delayed due to an algorithm that dropped readings of "zero" from the data on the assumption that it was some kind of error.
If you think our data models are perfect and humans make no mistakes, you can believe what our news stories tell you. If you don't believe that, then the answer is that "We don't actually know as much as we like to pretend we do."
(insert references to The Incredibles and Edna asking "Do you know where he is?" https://www.youtube.com/watch?v=OqMxPw6MVzY)
Even Seattle, which is robustly protected by its geography, is suffering anomalously high temperatures. Few people have air conditioning because most days rarely exceed 25°C. We are looking at 45°C on Monday, which is a once or twice per century occurrence.
Australians rarely have basements, but I wonder if this could be part of the solution long term. I have seen homes in the desert with huge concrete slabs inteded to operate as heatsinks/regulators, perhaps a concrete basement could do the same thing.
Even if homes had a lot of thermal ballast by construction, long runs of high temperatures like now require air conditioning. Something like 25% of homes, mostly newer ones, have air conditioning. It simply has not been needed historically. If there are a few days of 30°C temperatures, you opened a window. This current weather system is running much hotter and much longer than traditional Seattle summer weather.
I suspect there’s a better way to say that in jetstream but I neither speak newscaster nor climatologist :( Instead I’ll try to describe what the arrows in that cycle look like to me:
The climate spikiness from NorCal wine country moved up to Seattle. The flooding rains moved to Indiana. The endless drought expanded from Arizona to California. And all the weather systems got a jolt of energy, widening the extremes in all locations.
I think the trend is pretty clear.
Tldr, climate change is making many (but not all) of recent extreme weather events more likely or more extreme.