《史记·七十列传·南越列传》
正遇上酷暑潮湿的气侯，士卒中的多数人都得了重病，致使大军无法越过阳山岭。
会暑湿，士卒大疫，兵不能逾岭。
It just so happened that there was a period of hot, humid weather, and this caused many soldiers to fall seriously ill, rendering the army unable to cross Yangshan Pass.