After the East, the sun has moved to the Tropic of Cancer, but why is it getting colder and colder in the north?

If we only consider the position of the sun, the theory is this: the earth absorbs the heat of the sun during the day and releases it at night. In winter, the days in the north are short and the nights are long, and the heat emitted is greater than the heat absorbed, so the weather is getting colder and colder. After the winter solstice, the nights begin to get shorter and the days begin to get longer, but the nights are still long and the days are short. Although the heat absorbed by the ground began to increase, it still didn't give off so much heat, so it will continue to get cold. The movement of the sun to the tropic of cancer only slows down the cooling rate, and it has not yet reached the time of warming. Regardless of other practical factors, the temperature began to rise only after the vernal equinox, when the day was longer than the night.

In fact, the ground can be stored for a period of time after absorbing heat, and it will not be clean instantly. The ocean will absorb more heat. Air can keep warm, and it can also make the ground not cool down so quickly. Moreover, the air will flow, and the global climate will affect each other, which is conducive to warming, so the temperature will start to rise before the vernal equinox. But just after the solstice in winter, the temperature continues to drop.