"Fire flows in July" turns out to be a poem in the Book of Songs: Fire flows in July, and clothes are given in September. The general idea is: Whenever a star named 'Fire' appears in the western sky at dusk in the seventh month of the lunar calendar, the heat begins to subside. By September it will be cold, so you need to wear more clothes. (The star named 'Fire' is not Mars, but three stars in the Scorpio constellation in modern astronomy, belonging to the fifth star of the Eastern Qi constellation. 'Liu' means moving downward, and by the dusk of the seventh lunar month, it has moved to the western sky, so it becomes 'July Flowing Fire'.