Last month was the hottest September on record, with many cities, including Seoul, seeing a heat wave go onto early fall, the state weather agency said Tuesday.The average nationwide temperature recorded 24.7 C last month, marking the hottest September since nationwide weather observations began in 1973, and a record 4.2 C higher than previous years, the Korea Meteorological Administration (KMA) said.On most days, the daily average temperature surpassed that of previous years last month, with 46 out of 66 weather observation spots setting records as the hottest-ever September.The sea surface temperature in waters near South Korea also reached the highest in a decade, recording 24.7 C last month, up 3.2 C from the average in the past decade.The KMA pointed to a pressure system akin to that of summer as reasons for the belated heat wave, particularly the Tibetan high that developed further than normal years.Source: Yonhap News Agency