Ruili has a warm humid subtropical climate (Köppen "Cwa"), and is generally humid. Summer is long and there is virtually no "winter" as such; instead, there is a dry season (December thru April) and wet season (May thru October). A drier heat prevails from February thru early May before the onset of the monsoon from the Indian Ocean. The monthly 24-hour average temperature ranges from in January to in June, while the annual mean is . Rainfall totals about annually, with nearly 70% of it occurring from June to September.