The agency issued an alert just after 8 a.m. Friday, Yonhap News Agency reported.
Solar flares, a temporary local increase in brightness, release large amounts of energy that increases the ionization of Earth's upper atmosphere. That disrupts shortwave, high-frequency transmissions and can also affect satellites and cause problems for astronauts.
The U.S. Space Weather Prediction Center said the flare was the brightest so far this summer, Space.com reported.
Swim Week Miami Beach 2014 [PHOTOS]