South Korea on Sunday issued its first "grave heat wave" warnings for the southeastern cities of Gyeongsan and Pohang under a new highest-level alert system introduced last month to warn of extreme heat. The high-level warnings took effect in the two cities at 10:00 a.m., officials said, after temperatures soared to 39.9 C in Gyeongsan and 37.2 C in Pohang the previous day. Temperatures were again expected to reach 39 degrees C in both cities Sunday. The grave heat wave warnings issued in Gyeong