Because the autumn is crisp and fat! ! !

Chinese online dictionary:

Season for other animals in northwest China.

qigāo máféI

[Explanation] Autumn is crisp and the horse is fat. In ancient times, it refers to the season of external activities in northwest China.

[Source] Song Ligang's "Jingkang Biography" Volume 3: "I am afraid that the autumn will be high and the horse will be fat, and then I will make a promise."

Other cities, such as Andijan, Ili, Hami and Gurkha in the west, and Heilongjiang in the east, have bundled goods. ★ Qing Yu Zheng Xie's Guisi Draft Russian Affairs Series.