What kind of weather changes does July filariasis refer to?

"July filariasis" means that the weather is getting cold gradually, which means that the weather turns cold in July of the lunar calendar, and just after dark, you can see the big Mars falling from the west.

Source: The Book of Songs, Wind and July

Selected paragraph:

Fire is full in July, and clothes are delivered in September. The first day I was fat, the next day I was fierce. No clothes, no brown, why die? On the third and fourth day, I stood on tiptoe. With my daughter-in-law, we are very happy to see each other in the south.

Translation:

In July, the fire went down to the west, and in September, women sewed cold clothes. 1 1 the north wind blows hard in the month,1the cold wind blows hard in February. How can we spend the end of the year without good clothes and coarse clothes? In the first month, we began to hoe and plow, and in the second month, we went to farm. Tianguan was very happy, took his wife and children and sent the rice to the sunny land.

Appreciation of poetry and prose

July is the earliest monthly poem in China. It is said that it was written by Zhou Gongdan. According to modern textual research, it should be written by farmers in the Western Zhou Dynasty, describing the general situation of farming in each month of the year (now Xunyi County, Shaanxi Province). Selected from China 1 The Book of Songs, it is the longest poem. See Zhonghua Book Company 1979 "Righteousness Photocopying of Ruan Yuan Thirteen Classics Notes on Mao".

This poem is 300 years earlier than Heavenly Farming written by the Greek lunar calendar, but its contents in agricultural phenology are far richer than Heavenly Farming, which shows that China had understood the monthly relationship among climate, social activities and natural phenomena in considerable detail 3000 years ago.

Refer to the above? Baidu encyclopedia-July filariasis