This year's first tropical night occurred in Gangneung, Gangwon Province on Friday.

It's the earliest tropical night ever reported in the Gangneung area since related data began to be compiled for the region in 1973. Last year the area didn't see a tropical night until June 23rd.

Tropical nights occur when the lowest temperature between 6 p.m. and 9 a.m. the following day stays above 25 degrees Celsius.

Nationwide, it's the second earliest tropical night ever after May 16th in Pohang last year.

The Korea Meteorological Administration explained that high temperatures during the day didn't sufficiently drop after sunset due to the geographical features of the east coast Gangwon Province.