It was because of heat dome. 103 deg F in Arctic circle as of Jun. 23, 2021. What's happening is that the winds which circulate continually around the Arctic

It was because of heat dome. 103 deg F in Arctic circle as of Jun. 23, 2021. What's happening is that the winds which circulate continually around the Arctic Circle, which are called "jet streams," are being destabilized. Normally they're lines encircling the globe, but they're becoming wiggly, deviating North and South quite far. Current global models used for regular forecasting don't include these dynamic effects. I don't know what models do, but there is talk of "quasiresonant" behavior in the Rossby waves. This refers to a particular type of differential equation, or whatever (I'm no math genius). Obviously a lot more is going on, but I'm also no weather genius. I just thought you might find it interesting. Another point is that the specific wrinkle which caused the so-called "heat dome" was supposedly the result of heavy flooding rain all over China occurring on June 22-23. This somehow "added energy" to a ridge of high pressure which traveled along the jetstream path. When that ridge hit the wiggle in the jet stream it curled into a circle and trapped the weather. Apparently these general effects explain phenomena over the entire hemisphere. I don't understand it very well, but it is fascinating.