When is the hottest day in summer?

The dog days are the hottest time of the year. The dog days are characterized by high temperature, low pressure, high humidity and low wind speed, which is the hottest season in a year. This is because, in summer, the day is longer than the night, the day is longer and the sunshine time is longer. The heat absorbed by the surface is far greater than the expenditure, which makes the heat accumulated on the surface increase day by day and the temperature continues to rise. In midsummer, that is, in dog days, the accumulation of surface heat reaches its peak.

In summer, there is much rain and high air humidity, and the heat capacity of water is much larger than that of dry air, which is also one of the important reasons for the sultry weather. But the dog days are called "dog days" because there are also many cold factors. The dog days are the hottest thirty or forty days in a year in the Central Plains. The dog days are calculated according to the lunar calendar, between the middle and late July and the early August of the solar calendar.

Extended data:

Incubation time—

The time of accommodation is not fixed every year, and the length of accommodation is also different. You need to check the almanac to calculate it. Simply put, we can use the formula of "Xia San Geng" to express the lodging date, that is, from the third Geng day in Xia Hou, the initial lodging is 10 day, the intermediate lodging is 10 day or 20 days, and the final lodging is 10 day. In ancient China, the "trunk-branch calendar" was popular, and 60 groups of different names were used to record dates with 10 heavenly stems and 12 earthly branches, which were recycled. The day with the word "Geng" is called "Geng Day".

The word "Geng" in Geng Day is the seventh word in "A, B, C, D, E, Ji, G, Xin, Ren, Gui" 10 day, and it is repeated every 10 day. Starting from the summer solstice, according to the date of trunk, the third Geng day is the first, the fourth Geng day is the middle, and the 1 th Geng day after beginning of autumn is the last.

When there are four Geng days between the summer solstice and the beginning of autumn, the middle part is 10 days, and when there are five Geng days, the middle part is 20 days. It seems that the emergence of Gengri will affect the length of the first half sooner or later, so there will be 30 days in some years and 40 days in some years.