Iwamizawa's winters are harsh, with temperatures often plummeting below -20°C in January and February. Spring brings gradual warming, with April marking a significant increase in temperatures as the mercury rises to averages of around 7°C. Summers are warm to hot, with July being the hottest month, averaging 23°C, while autumns are mild, with September and October experiencing comfortable temperatures ranging from 7°C to 27°C. By November, temperatures start to dip again, but December is still relatively cold, with averages around -2°C.