Winters in Iwakuni are cool and relatively mild, with temperatures ranging from freezing cold to moderate warmth. January is the coldest month, with average temperatures around 5°C, while February and December have similar temperatures. Springs bring gradual warming, with March's highs reaching up to 23°C and April averaging around 15°C. Summers are warm to hot, with July and August experiencing peak temperatures above 35°C, although June and September also experience high heat. Autumns are mild, with October seeing a drop in temperature before the cooler months return.