Sometime last week to ten days ago I recall seeing that the south western USA was experiencing a heat dome effect. Literally a cap of heat that sits over the land and doesn't move. It prevents sea breezes from moderating the temperatures and actually draws intense hot air from the interior. There is no cool down at night and so it just builds day by day.
I thought " those poor people!"
Well, a week later and it seems that western Canada has one and we're under it right now. The link is to a local new article on the heatwave: Heat Dome Article