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Japan’s traditional calendar includes 24 seasonal days that mark when various changes in the weather occur. October 23 is Soukou, or ‘descending frost’ when the temperatures start becoming cold enough to see layers of light ice on the ground. Clouds of fog appear here on Lake Kizaki in Nagano Prefecture as warm air passes over the cold water and nearby farms.
The National Diet Library has more in-depth information about the traditional Japanese calendar, its origins, and the relationship to the modern-day calendar. To learn more, please visit their site: https://www.ndl.go.jp/koyomi/e/