The amount of South Korea classed by Greenpeace as a "high temperature area" has more than doubled since 2010.
In the latest Greenpeace report released on Thursday, areas with an average surface temperature above 30 degrees Celsius in August soared to 27 percent of the country between 2011 and 2019.
It's a big jump from the 12 percent recorded during 2002 to 2010.
Surface temperatures for some parts of the country, including Seoul, rose by more than one.five degrees.
The temperatures of streams and rivers in the capital region also climbed.
Seoul city said that the average maximum water temperature of the Han River's main tributary in Seoul was nearly 27 degrees last month, up two.six degrees from the average between 1994 and 2020.