Most places in South Korea received three to four times more rainfall last week than the average precipitation recorded in the same period in the last 30 years.
At least 30 people are dead and 12 missing after landslides and flooding brought on by a week of heavy monsoon rains hit South Korea.
The government is issuing warnings of more downpours in the coming week.
Rain on Friday and Saturday left more than 3,700 displaced as it flooded residential areas, roads and farming fields.
Nearly 5,000 people had been evacuated as of 1930 GMT on Saturday.
The Ministry of the Interior and Safety said the Seoul area and the southern region are expected to receive more heavy rain on Sunday and Monday.
Weather official Woo Jin-kyu said most places in South Korea received three to four times more rainfall last week than the average precipitation recorded in the same period in the last 30 years.
More flood and landslide warnings
About 100 metres of levee collapsed at the Seomjin River in the southern edge of the peninsula and flooded the area with about 1,900 people evacuated in the province.
The country's forestry agency has raised landslide warnings to its highest level in every region except the holiday island of Jeju.
Five homes were buried in a landslide on Friday from a mountain behind a village in Gokseong, South Jeolla province, killing five people.
Twelve local flights were cancelled at the regional Gwangju airport near the southwestern tip of the peninsula after the runway was flooded, according to Yonhap news agency.
Seoul warns residents
The city of Seoul warned people to stay away from basements, valleys and rivers.
South Korea's longest monsoon on record was 49 days in 2013.
Current weather forecasts predict that this year's monsoon may last longer.
In neighbouring North Korea, state media Korean Central Broadcasting also warned of additional heavy rains in areas already hit by floods, according to Yonhap.
Following leader Kim Jong-un's flood relief inspection reported on Friday, KCNA said on Saturday that Pak Pong-ju, vice-chairman of the state's highest decision-making commission, inspected damage to submerged fields and crops in southwest regions of the country.