Great cold, like slight cold, is a solar term indicating the degree of cold weather, and great cold is extremely cold weather. The great cold solar term is from March 9 to April 9, and the cold wave frequently goes south, which is the coldest season of the year.

Although the winter solstice solar terms are the lowest in the northern hemisphere, the coldest time of the year is the slight cold and great cold solar terms after the winter solstice solar terms, especially the great cold solar terms.

This is because after the winter solstice, the direct point of sunlight will gradually move northward, but in the following time, the direct point of sunlight will always be in the southern hemisphere, and the heat in the northern hemisphere will always be lost, and the heat absorbed during the day is still less than the heat released at night. Therefore, after the winter solstice, the temperature in the northern hemisphere will continue to decrease, and the temperature will be the lowest during the severe cold solar term.

Severe cold phase 3

In ancient China, the Great Cold was divided into three stages: "One stage is chicken milk; Second, the symptoms of bird disease; Three times, the water is strong. " It means that in the cold season, spring air germinates and chickens can hatch.

Five days later, birds flying far away, such as eagles and falcons, became fiercer and swifter, hovering in the air and foraging everywhere; After another five days, the ice in the water has frozen to the center of the water, freezing up and down, extremely cold.

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