‘Sanjiu’ (the third ‘nine-day’ period) is part of China’s traditional ‘Shu Jiu’ (Counting in Nines) winter custom, occurring between the 19th and 27th days after the Winter Solstice. It is widely regarded as the coldest time of the year, reflected in the popular saying, ‘The coldest days fall in Sanjiu.’ But does the cold truly end after Sanjiu? The answer is no.Although Sanjiu typically marks the peak of winter chill, actual temperatures depend on geographic location, atmospheric patterns, and yearly weather conditions. In some years, strong cold fronts or prolonged low temperatures may persist into ‘Sijiu’ (the fourth nine-day period) or even ‘Wujiu’ (the fifth). For instance, northern China might experience another cold snap after Sanjiu, while southern regions can still feel bone-chilling damp cold due to high humidity.From a meteorological perspective, although solar radiation gradually increases after the Winter Solstice, the Earth’s surface continues to lose more heat than it gains until around ‘Wujiu’ or ‘Liujiu’ (the sixth period), when noticeable warming usually begins. Therefore, Sanjiu’s end doesn’t guarantee immediate spring-like weather—people should continue dressing warmly and remain cautious against cold-related health risks.In short, while Sanjiu is often the coldest stretch, winter’s grip may linger. Understanding the relationship between traditional seasonal markers and real-world weather helps us better prepare for daily life and travel.
“三九”是中国传统节气文化中“数九寒天”的第三个九天，通常出现在冬至后的第19天到第27天之间，被认为是一年中最冷的时段。民间有“冷在三九”的说法，意味着此时气温达到全年最低点。然而，“三九”过后是否还会冷？答案是肯定的。虽然“三九”常被视为寒冷的顶峰，但受地理位置、气候系统和当年天气形势影响，部分地区在“四九”甚至“五九”期间仍可能出现强冷空气或持续低温。例如，北方地区在“三九”之后若遭遇寒潮，气温可能再度骤降；而南方则可能因湿冷效应，在“三九”后仍感觉寒冷刺骨。此外，从气象学角度看，冬至后太阳直射点虽逐渐北移，但地表热量收支仍处于“入不敷出”状态，直到“五九”或“六九”前后，气温才会明显回升。因此，“三九”过后并不等于立刻回暖，公众仍需注意防寒保暖，不可过早减少衣物。总之，“三九”虽冷，但寒冷未必就此结束。科学看待节气与实际天气的关系，有助于我们更好地安排生活与出行。
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