Isesaki's winters are cold and occasionally frigid, with temperatures often below freezing. As the season progresses, temperatures gradually warm up in spring, with highs reaching into the mid-20s Celsius by April and May. Summer is hot and humid, with July being the hottest month on average, while September marks a return to milder temperatures. Autumn brings a slight chill, but temperatures remain relatively mild until November, when they begin to drop again.