With a monsoon front approaching, heavy rainfall is expected throughout this week, the weather agency said.

On Sunday, many cities nationwide saw much needed rain, which was delayed about 10 days compared to last year, along with cooler daytime temperatures.

Around 80 to 150 millimeters of rain poured down in Seoul, while other regions saw about 10 to 100 millimeters of rain.

Due to continued rain throughout a day, the Seoul Metropolitan Government closed off traffic to Cheonggyecheon Stream.

A daytime high nationwide went down by 3 to 4 degrees Celsius, hovering around 26 degrees in the capital. Morning low hit 23 degrees in Seoul.

The Korea Meteorological Administration said sporadic rain showers are expected to linger until the first week of July.

The KMA said up to 150 mm of rain is predicted to pour down nationwide until Wednesday and the monsoon front will bring more rain in the southern cities like Gwangju and Busan later in the week.

But the agency said this summer will see a dry monsoon season, with higher temperatures and less showers. It predicted some 289 millimeters of rain in July, not enough to bring relief to drought areas.

As heavily developed rain clouds are making their way into a stretch of the western Pacific Ocean and influencing skies of East Asian countries, the KMA said the heavy rain will hit Gyeongsang Province hard, while Gangwon and Gyeongsang provinces could experience loud thunder and lightning along with rain.

As of Sunday afternoon, a heavy rain advisory is issued in Gapyeong, Gangwon Province and some cities in Gangwon Province. A heavy rain advisory is issued when at least 70 mm of rain is predicted to pour down for six hours.

A preliminary rain alert was issued in metropolitan areas like Seoul and Incheon and Chungcheong Province and some cities in North Gyeongsang Province as these regions are expected to see up to 200 millimeters of rain. 

Weather forecasters encouraged people to be aware of accidents amid the torrential rain accompanied by thunder, and be prepared for the heavy downpour to cause floods, traffic jams and the disruption to facilities.

By Kim Da-sol (ddd@heraldcorp.com)