Will COVID-19 Get Worse In the Winter?

We’re about to head into our first full winter season in the Northern Hemisphere while simultaneously battling the COVID-19 pandemic. Cases are already rising across parts of the U.S., and many are worried that the colder weather will bring another wave of infections. 

Experts say there’s good reason to be concerned—but there are things we can do to mitigate our risk.

What Makes COVID-19 Worse In the Winter?

There are two factors to consider when we think about COVID-19 in the winter: the biology of the virus and human behavior.

When it comes to the virus itself, experts say temperature and humidity might play a role in how well COVID-19 can survive in the air, but much is still unknown. There’s some evidence that shows colder, drier air promotes the lifespan of the influenza virus, but it’s too early to say if SARS-CoV-2, the virus that causes COVID-19, will behave the same way, Eric Bortz, PhD, an associate professor of biological sciences at the University of Alaska Anchorage, tells Verywell. 

Until we know more, Bortz says the winter season is largely concerning because of our own behavior. When it’s dark and snowy, there’s less opportunity to socialize outside, especially when activities like outdoor dining and park get-togethers are limited.

“People are together indoors a lot more in the winter…and having longer, more sustained indoor contact,” he says. 

Peter Gulick, PhD, an infectious disease expert and associate professor of medicine at Michigan State University, tells Verywell winter conditions create a prime environment for COVID-19 to spread. The cold forces many people to bring outdoor activities inside.

If someone infected with COVID-19 coughs or sneezes outside, wind or a natural breeze can dilute the virus. A study published in May also found that natural sunlight can inactivate COVID-19 particles on surfaces.

But when you’re indoors, you don’t have the same natural conditions. Opening windows and doors can promote better ventilation, but these options may not be feasible when it’s below freezing outside.

Winter also comes hand in hand with the holidays, which typically brings larger groups of people together. While people understandably want to see their loved ones, socializing indoors poses risk—especially if people don’t wear masks.

“The virus has to be transmitted to people in order to survive better, and it’s transmitted at a much easier rate if you’re in an enclosed environment versus an environment where you’re out in the open,” Gulick says. “When you look at the indoors…and have air recirculated inside a room, the virus just perpetuates itself and recirculates in that environment.”

Cold and Flu Season 

On top of concerns around a surge in COVID-19 cases, winter is cold and flu season. Pneumonia also peaks in the winter.

Bortz says the same groups who are at greater risk of severe COVID-19 are also vulnerable to the flu, including older adults and people with hypertension or obesity.

It is possible to get both the flu and COVID-19 at the same time, meaning it’s important people head into the winter understanding the risks and protect themselves.

This winter is concerning, Bortz says, as “severe flu cases can end up in the hospital—especially young children and those who are older” which can further strain healthcare systems that are already stretched due to COVID-19 cases.

“You run out of ICU space, your healthcare workers get exhausted, and you put a lot of pressure on the healthcare system,” he says. “So we’re looking at potentially this sort of double whammy.”

One silver lining based on countries in the Southern Hemisphere who just experienced the winter season, Bortz says, is that flu cases didn’t spike the way they have in previous years. He points to Australia and Chile; both countries had mild flu seasons.

“It’s thought that all the control measures for COVID-19 also reduced the spread of the flu,” he says.

But because the Northern Hemisphere has a much larger population, and the U.S. is allowing more travel than a country like Australia that implemented a travel ban, it’s too early to say if we will see similar results.

“Maybe our flu season will be a little bit [better], but on the other hand, we have a large segment of the population that doesn’t really observe [COVID-19] guidelines,” Bortz says.

Ways to Protect Yourself and Others

Masks are vital to preventing the spread of COVID-19 at all times, but they’re especially important to wear as we head into the winter and face cold and flu season.

Gulick says masks need to fit properly—covering the nose and mouth, with no gaps at the sides. Your mask will act as a layer of protection, helping block escaping virus particles from getting to you. 

“Instead of getting, say 1,000 viral particles directly in your face, you’re going to get maybe 100, maybe even less than that,” Gulick says. “So the amount of virus is going to be much less; it might not be enough to cause any infection at all.” 

People should also follow local public health guidelines and practice social distancing. Depending on where you live, there might be restrictions on group gatherings. If you’re sick, it’s best to stay away from others, Bortz says.

“For any kid or adult who has respiratory disease symptoms, even if they’re very mild, at this point the recommendation is to isolate, quarantine, and stay away from other people until you’re over it,” he says.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.