A little rain last weekend helped cool things off in Korea, but now the heat is back and so is the humidity.
Heat wave advisories have been issued for almost the entire country, with the average high today above 35 degrees Celsius.
Water temperatures along most of the nation's coast are high too, some above 28 degrees, which is a threat to fish stocks.
The heat's been affecting the health of people, too, with more than one thousand heat-related illnesses reported this summer, which is more than double the number last year.
The health authorities say UV ray levels are very high right now, and are urging people to avoid spending time outside especially from 10 AM to 3 PM.