Which month is the hottest in a year?

Every year on July 22nd or 23rd of the solar calendar, when the sun reaches120th degree, it is the summer solar term, and it is the last solar term in summer. The summer solar term is just around the Mid-Autumn Festival in the dog days, which is the hottest period of the year, with the highest temperature and the fastest growth of crops. At the same time, various meteorological disasters such as drought, waterlogging and wind disasters are also the most frequent in many areas.

"Three volts" refers to the first, middle and last three volts, that is, from mid-July to mid-August. 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 main factor affecting the temperature is the intensity of solar radiation, and the light and heat of the sun can not directly raise the temperature. The heat energy directly absorbed by various gases in the air is only about 14%, while about 43% of the heat energy is absorbed by the ground. After the ground absorbs solar radiation heat, it is conducted into the air through radiation, convection, turbulence and other forms. The result of this upward heat transfer is the main reason for the temperature increase. Therefore, the increase of ground temperature is mainly the result of absorbing solar radiation energy.