From the normally chilly Russian Arctic to the traditionally sweltering American South, big swaths of the Northern Hemisphere continued to sizzle with extreme heat as the start of summer more resembled the dog days of August.
In the United States a heat dome of triple digit temperatures in many places combined with high humidity oscillated from west to east. On Thursday, at least eight states hit 100 degrees (37.8 degrees Celsius) and at least nine high temperature marks were set or broken, according to the National Weather Service, which held 30 million Americans under some kind of heat advisory.
