Winters in Sanyo-Onoda are cold and unpredictable, with temperatures fluctuating between freezing lows and mild highs. January is the coldest month, with temperatures averaging around 5°C, while February sees a slight warming trend, but still experiences chilly nights. As spring approaches, March brings a steady rise in temperature, reaching averages of 12°C, followed by April's pleasant warmth, with average highs of 15°C. Summers are hot and humid, with July being the warmest month, averaging around 27°C, while autumn returns to cooler temperatures, similar to those experienced in winter, with October's averages mirroring January's.