Khlong Yai has a tropical monsoon climate (Köppen climate classification Aw) influenced by the nearby Cardamom Mountains, which amplify the summer monsoon. While no month is truly dry, a short dry season runs from December to January. Rain increases somewhat from February to April, and then the main monsoon season begins in May, lasting until October. The monsoon season features torrential rain, with over falling in August alone, and over falling in each of June and July. The rains ease in November, although significant rainfall may still occur. The highest monthly rainfall recorded from 1961 to 1990 was a total of in August.