How do we describe 九九 in english In Chinese lunar calendar, starting from 冬至, which was yesterday, you can count 9 days as the first 9 days, and subsequently second, third,...,until ninth nine days, a total of 81 days. After you count 81 days, the weather starts getting warm. My question is, are there specific english translations associated with this? I tried to describe it to other people, but find it too difficult to explain. How would you describe it to other people?
This Beijing Tourism page has an English article about the 9 nine-day periods:

Nines of Winter in China
People in China talk about winter coming in nine periods and each period is 9 days long, which begins from the Winter Solstice. After 9 nine-day periods the weather becomes warmer and spring will be on its way.
The 3rd nine-day period is called ‘Sanjiu’ in Chinese, which refers to the 19th-27th days after the day of the Winter Solstice. There is an old saying in China that goes, &quot;The days of the Sanjiu period are the coldest days.&quot;
There is a famous folk song about the Nines of Winter (called ‘Shujiu’) recording changes in the weather:
1st nine days, 2nd nine days, don’t take hands out of your pockets;
3rd nine days, 4th nine days, you can walk on ice;
5th nine days, 6th nine days, willows at the river’s edge start to sprout;
7th nine days, ice dissolves and water flows in the river;
8th nine days, wild geese fly back to northern areas;
9th nine days and the following days, farm cattle start to work in the field.