Autumn high and refreshing, describing the autumn sky clear and clean climate cool and pleasant.

The term comes from Du Fu's "Cui's East Mountain Cao Tang" in the Tang Dynasty: "Love you Yushan Cao Tang quiet, high autumn cool air phase fresh new."

The reasons for the high and refreshing autumn are as follows:

1. Because of the blue sky during the day and the cloudless sky at night, the heat on the ground can be freely dispersed. Coupled with the fall, the day is short and the night is long, the sun's heat absorbed during the day, it is not enough to make up for the heat dispersed at night, so the ground temperature is gradually reduced down, but the reduction is not much, so it is the beginning of the cooler than the cold, the temperature is pleasant.

2. After the fall, people sweat less, even if a little sweat, due to the lack of moisture in the air, dry and cool air so that the sweat on the body quickly evaporated, the clothes on the body have a cool feeling, so give people a feeling of fresh air.