This weekend has been a scorcher in parts of Europe, the U.S. and Asia.
In Spain and France, it got above 40 degrees Celsius.
In the United States, more than 20 million people were under heat alerts in 16 states.
Northern and central China got into the 40s as well, with the authorities advising people to avoid activities outdoors.
Heavy rains caused flooding in China's south, disrupting the lives of nearly half a million people.
The south of China has seen its worst flooding in decades, with Guangdong Province on Tuesday raising its alert to the highest level after days of rainfall.
In Japan on Saturday, more than 60 regions,
including Tokyo, saw temperatures higher than 35 degrees.
According to the Yomiuri Shimbun, this is the earliest in the summer for it to get that hot in Tokyo since data were first compiled in 1875.
The Korean capital of Seoul on Sunday recorded its highest overnight low in 25 years.
It never got below 24.6 degrees.
In the city Incheon, the overnight low was the highest in 117 years.
Decades-long records broken in other cities too.
Heat waves are a phenomenon that's been occuring more frequently in recent years around the world, as shown by a study by the American Meteorological Society.
The average number of days between May and September with at least one large heat wave in the Northern Hemisphere has doubled from 73 in the 1980s to 152 in the 2010s.
And the number of days with two or more heat waves in different parts of the hemisphere was seven times higher.
Some scientists say more extreme weather events will accompany these heat waves.
They say a slowdown of air currents can cause heat waves to last longer, as temperature differences narrow, keeping weather systems from moving around the planet.
They warn global warming could lead to disease, death and poor harvests, which could aggravate global food shortages.
Lee Rae-hyun, Arirang News.