Saito has a humid subtropical climate (Köppen climate classification Cfa) with hot, humid summers and cool winters. The average annual temperature in Saito is . The average annual rainfall is with June as the wettest month. The temperatures are highest on average in August, at around , and lowest in January, at around . The highest temperature ever recorded in Saito was on 31 July 2013; the coldest temperature ever recorded was on 27 February 1981.
