YANGSAN, South Gyeongsang Province — The streets of Yangsan, where Korea recorded its highest temperature ever at 42.5 degrees Celsius on Sunday, were nearly deserted except for delivery riders rushing between orders. Outside a restaurant in Jungbu-dong, a delivery rider in his 40s repeatedly shifted his feet while waiting to pick up food, unable to bear the heat radiating from the sun-scorched asphalt. As the heat wave drove a surge in food delivery orders, he was fully equipped with cooling arm sleeves, a cooling vest and a neck cooler, but sweat still poured down his face. Removing his helmet to wipe away sweat, he said, "It's so hot that I can't even stand still outside. The whole city feels like a giant boiling cauldron." Yangsan has been gripped by an unprecedented heat wave after shattering the nation's all-time temperature record. The city has been under the highest-level heat wave warning for nine consecutive days since July 25. Temperatures have exceeded 40 C for five straight days since Wednesday, peaking at 42.5 C at 1:26 p.m. Sunday, the highest temperature ever officially