Temperatures soared to another record for August on Monday, with 38.4 degrees Celsius in Miryang, South Gyeongsang Province.
Many parts of the south saw temperatures above 35 degrees, including Daegu (37.4), Ulsan (36.5) and Jeonju (35.2).
Sultry weather will continue in the south until Wednesday, with rain on Thursday afternoon expected to drive down the day's high to around 30 degrees, the Korea Meteorological Administration said.
A hot weather warning was issued in Seoul as temperatures are expected to rise to 33 degrees on Tuesday and Wednesday.
A low pressure trough passing over southern parts will bring rain across nation starting Thursday afternoon, a weatherman forecast, but sweltering weather could return in September.