It didn't start to pick up until September.

"Jiujiu", also known as "shǔjiǔ", is a folk solar term in winter in China. The "number nine" began the day after the "winter solstice" in late February and early February of 65438. When the custom of "counting nine" originated, there is no exact information at present. However, it was popular at least in the Northern and Southern Dynasties. "Liang Chao Shu Jing Chu Chun Qiu" records: "The winter solstice is 998 1 day, which is the end of cold." Count nine cold days, that is, from the solstice of winter, count nine every nine days until the eighty-first day, and the weather will warm up.