The government said the victims include 13 dead and two missing in the past two days, as the country battles through its longest monsoon since 2013.
Some areas have experienced more than 40 consecutive days of rain.
The downpours left more than 3,700 people displaced on Friday and Saturday alone, as residential areas, roads and farm fields all suffered devastating flooding.
And the capital, Seoul, and other areas in the south have been warned by the Ministry of Security that even heavier downpours are expected on Sunday.
Landslide warnings remain in place at the highest level for every region except Jeju Holiday Island.
Meteorological official Woo Jin-kyu said most places in South Korea had received three to four times more precipitation last week than the average precipitation recorded during the same period over the past 30 years.
Trapped residents were photographed using rubber rings to stay safe in Hadong County in the southeastern southeast, as cows struggled to keep their heads above the water in the southeast. west of Gurye.
Some also had to be rescued from their cars, being stranded by flooding on the roads.
About 100 meters of dike collapsed on the Seomjin River at the southern edge of the Korean Peninsula on Saturday, forcing about 1,900 people to be evacuated from the local area.
Five houses were buried in a landslide from a mountain behind a village in Gokseong, South Jeolla province on Friday.
killing five people and demanding more to be rescued.
Forecasters fear the monsoon will eventually eclipse the length of that seen in 2013, which at 49 days is the longest on record in the country.
North Korea was also affected by flooding, with growing concerns over crop damage.
Chef Kim Jong Un visited a town on the border with its neighbor to the south on Friday to inspect the damage.
There, torrential rains destroyed 179 homes and flooded rice paddies – but there were no deaths, according to the official KCNA news agency.
North Korea’s ruling party newspaper Rodong Sinmun cited a study that said rice and corn would suffer if crops were underwater for just two or three days.