What is Kokushobi, Japan’s new word for deadly extreme heat?

It's so hot in Japan that the country invented a word for it, really. Deadly heat waves have transformed a major part of the world into a plot of a sci-fi movie where people are cooping up at homes and fighting for air conditioners at marts. Large parts of East Asia have been gripped in a deadly heat wave, bringing the hottest temperature on record in South Korea and complicating earthquake recovery efforts in Japan.The land of the rising sun experienced its first "cruelly hot day" toward the end of July, in a historic heat wave that caused multiple cities to be scorched with temperatures over 104 degrees Fahrenheit. Tokyo’s average daily temperature that month was 90 degrees Fahrenheit, which would feel like 110 degrees when accounting for humidity. The “cruelly hot day,” was introduced by Japan’s meteorological agency this year in anticipation of a sweltering summer.