When is the hottest?

After the summer solstice, although the days are getting shorter and the nights are getting longer, the days are longer than the nights in a day. Every day, the ground absorbs more heat than it emits, and the temperature near the ground is getting higher every day. During the "three volts" period, the heat absorbed by the ground is almost less than the heat emitted, and the weather is the hottest. After that, the heat absorbed by the ground began to be less than the heat emitted by the ground, and the temperature gradually decreased. Therefore, the hottest time of the year generally appears in the "dog days" from the summer solstice. The summer solar term is the hottest solar term in a year. The ancient book "Twenty-four solar terms" said: "It is extremely hot in the summer." This is enough to explain the fiery degree of this solar term. The reason why it is extremely hot during the "Great Summer" is that since the beginning of summer, the heat absorbed from the ground sun during the day is more than that emitted at night, and the heat keeps accumulating. During summer, accumulated heat reaches its peak, so summer is the hottest.

At the hottest time of the day, the sun shines on the ground, making it hot, and the heat absorbed by the ground is released to heat the air. The temperature of air is mainly obtained indirectly from the ground. Although at noon in summer, the sun shines on the ground closest to direct light, and both the ground and the air are strongly heated, the heat released by the ground is less than the heat provided by the sun, so this is not the hottest time. After noon, the ground temperature can continue to rise until the heat released by the ground is equal to the heat provided by the sun, and the ground temperature can rise to the highest; The temperature rise near the ground must be obtained from the heat released from the ground, which takes time, so the hottest time in summer is not at noon, but at two or three o'clock in the afternoon.