A few snow flurries blew through the streets of Shanghai this week as temperatures dipped perilously close to freezing. Yet if you glance at the city’s young children, you might think they were planning a trip to Siberia. Along the middle and lower reaches of the Yangtze River, wintry weather, high humidity, and a lack of central heating have got parents digging out extra sweaters, coats, and scarves — sometimes bundling their kids in so many layers that they can hardly move.

A particularly virulent strain of winter flu has also left many children sick, saddling parents with an exhausting additional burden. But the kneejerk reactions of many cold-fearing Chinese parents are, if not complete bunk, then at least more beholden to tradition than to medical science.

Many Chinese parents are afraid of exposing their kids to the cold because common medical knowledge dictates that it weakens the immune system, leaving the body more susceptible to infections. As a result, parents assume that adding more layers of clothing is essential for staving off diseases.

But being too warm is dangerous, too. Children have high metabolisms and lots of energy, which means they tolerate the cold better than adults. Medical studies have revealed that keeping children too warm and staying too long in an excessively hot or stuffy atmosphere can lead to a lack of oxygen, high fever, heavy sweating, and dehydration. These are potentially life-threatening conditions, and stories of overheated children have occasionally attracted the attention of Chinese media. Yet the compulsion to block out the cold runs deep in Chinese tradition; indeed, wrapping kids up in extra layers is similar to the custom of zuo yuezi, or postnatal recuperation, whereby new mothers stay in bed for several weeks following childbirth. Some women have even suffered from heatstroke after well-meaning but misguided family members piled on too many heavy blankets.

While parents often go to great lengths to make sure their children are comfortable, traditionally minded grandparents tend to be the most overzealous. Parents in their 20s or 30s have more modern attitudes toward child care and personal health, and are therefore less likely to force their children to put on too many layers. But as millions of working moms and dads leave children in the care of their elderly grandparents, the older generation gets to determine the kids’ attire.

Part of the problem is that elderly people project their own vulnerability to the cold onto their grandchildren. Older people have slower metabolisms than kids and tend to be less active, which means they feel the cold more acutely. Concerned that the child feels the same, grandparents then throw on more sweaters and coats.

In addition, many grandparents retain memories of extreme hunger and cold. My mother was born in the 1950s in eastern China’s Zhejiang province, for example, and grew up in a time when food and clothing were scarce. She wore a single cotton-padded jacket throughout the winter, then pulled out the cotton and stitched it back up a thin summer jacket. While these memories are far removed from the relative abundance we see around us today, doting grandparents still prefer to see young children wear too much rather than too little.

Fear of the cold is perhaps best captured in a tenet of traditional Chinese medicine: the need to balance the body’s yin and yang, two opposite but complementary forces that result in good health if held in equitable amounts. The same philosophy states that this internal balance, in turn, mirrors balance in the external world, and in society as a whole. In winter, as the weather becomes colder, the amount of yin energy in the world increases; as a result, new sources of warmth — that is, sources of yang energy — are essential to maintaining good health. Aside from wrapping up warm, other traditional methods for staying healthy during the winter involve eating food with supposed yang properties, like mutton or ginger soup.

Even though traditional Chinese medicine does not advocate dressing too warmly, in practice people tend to focus more on building up yang energy. This is because yang constitutes a positive force: It connotes light, warmth, and vigor, and is therefore seen as somewhat superior to yin.

Of course, lots of Chinese habits for staying warm in winter — basking in the sunlight, bathing in hot water, or eating high-protein foods — are corroborated by modern medicine. However, they exist alongside less-viable health concepts — like the notion that an extra sweater is always preferable to none at all — and this creates a particular set of cultural expressions that evoke powerful feelings, beliefs, and compulsions.

But Chinese child care methods are evolving. Younger parents who spend ample time with their children are more likely to judge whether a traditional practice is good for their kids based on hard evidence rather than superstition. Many parents in their 20s and 30s now care less about what their children wear, recognize that catching colds and the flu can help the body build up resistance to disease, and focus on making sure their children eat healthily and get plenty of exercise. This culture shift may yet mean that fewer Shanghainese children will dress for an Arctic expedition when the mercury starts to plummet.

Translator: Katherine Tse; editors: Zhang Bo and Matthew Walsh.