Winter makes you more vulnerable to cold and flu viruses. Here’s what to do about it

You’ve probably heard “Don’t go outside in the winter with your hair wet or without a coat; you’ll catch a cold.”

That’s not exactly true. As with many things, the reality is more complicated. Here’s the distinction: Being cold isn’t why you get a cold. But it is true that cold weather makes it easier to catch respiratory viruses such as the cold and flu.

Research also shows that lower temperatures are associated with higher COVID-19 rates.

As a professor of nursing with a background in public health, I’m often asked about infectious disease spread, including the relationship between cold and catching a cold. So here’s a look at what actually happens.

Many viruses, including rhinovirus—the usual culprit for the common cold—influenza, and SARS-CoV-2, the virus that causes COVID-19, remain infectious longer and replicate faster in colder temperatures and at lower humidity levels. This, coupled with the fact that people spend more time indoors and in close contact with others during cold weather, are common reasons that germs are more likely to spread.

The flu and respiratory syncytial virus, or RSV, tend to have a defined fall and winter seasonality. However, because of the emergence of new COVID-19 variants and immunity from previous infections and vaccinations decreasing over time, COVID-19 is not the typical cold-weather respiratory virus. As a case in point, COVID-19 infection rates have surged every summer since 2020.

Virus transmission is easier when it’s cold

More specifically, cold weather can change the outer membrane of the influenza virus, making it more solid and rubbery. Scientists believe that the rubbery coating makes person-to-person transmission of the virus easier.