For millennial and fashion-conscious Chinese who wouldn't want to be seen wearing the same thick, quilted, padded red pajamas as their parents, in recent years thinner and more fashionable variations have appeared in stores.
But what do foreigners living in China think about this seasonal trend? Would they dare wear long johns under their daily clothes?
Indeed, the sight of long johns poking out of the bottom of Chinese people's pants has become a kind of joke or meme among Chinese netizens.
Long underwear was imported into China from the West. Long johns were first introduced in England in the 17th century, then became popular as sleepwear in the 18th century as migrants settled in the Americas. The modern two-piece design is credited to Myles Stanfield, a native of Nova Scotia, Canada, who patented his design in 1915.
But the use of long underwear depends on each foreigner's native country. In the Ukraine, where temperatures drop to minus 20 degrees in the winter, long underwear is essential.
"We wear it because it is too cold in the Ukraine. In every building we have a heater, but still we wear it because it is not warm enough," said Pavel, a Ukraine national.
Warmth versus fashion
In the US, however, heating systems are well-developed. Homes, apartments, cars, public transportation and offices are all constructed with built-in heaters. But in many central and northern states, like Maine, long johns are still worn just as they were in the 1800s.
Keri from Chicago, the US, said that she wears long underwear in the winter whenever she goes outside. "It is more important to stay warm than be fashionable."
"Maybe in places like New York City you might not see it as much," she added. "But somewhere like Chicago can get very cold," she explained.
Unlike the Chinese, who prefer their long johns all in one solid color such as red or flesh-toned, Keri likes to mix it up. "I will buy a plain color for underneath my pants, and for a shirt a pattern. A lot of people [in Chicago] wear patterned thermal shirts as their regular top shirt," she said.
Niels from the Netherlands, where winter sees temperatures drop to minus 10 degrees, said people there wear jeans, a T-shirt and a simple coat even when it's freezing.
"We wear thermal underwear only for skiing or snowboarding, but not during your regular day. Maybe at night, as a sort of pajamas. For us it would be a little bit uncomfortable. It's too tight," he said.
In Israel, where winters don't get much colder than 20 degrees, long johns are unheard of. "Our country is a warm country," Albert from Israel said. "It would be too warm to wear it underneath; a shirt and a light jacket are enough."
Good for health
According to Traditional Chinese Medicine (TCM), wearing long underwear is good for people's health. Zhang Ting, professor from Shanghai University of Traditional Chinese Medicine, said that wearing too few clothes, especially in the winter, can lead to a stagnation of vital energy and blood in the body.
Headaches, stomachaches, dysmenorrhea and arthralgia (joint pain) are symptoms that people (especially the elderly) can suffer if they don't insulate themselves in the winter.
Zhang also suggested the following advice to help guide newcomers through Shanghai's notoriously cold winters. "First, pay attention to your neck warmth, otherwise it may decrease blood circulation. The second is to pay attention to lower limb warmth, which could lead to frostbite, leg cramps and joint pain," Zhang said.
For sports enthusiasts, Zhang suggests not exercising excessively in the cold and not training too early in the morning.
"Fitness enthusiasts often sweat profusely in the winter [because they wear too much clothes], which is not good for their health. Since it is also very cold in the early morning, it is unnecessary to exercise too early. Wait until the sun comes out," the professor said.