COVID and cold weather: Experts explain why you should wear a mask outdoors in winter

People wear face masks as they walk along a street as light snow falls in Montreal, Sunday, November 22, 2020, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes

As winter weather sets in, many Montrealers are discovering that regularly wearing a mask outside is a good way to keep their faces warm.

Another bonus - if you’re already wearing it, you don’t have to clumsily displace your tuque to hook a mask over your ears before heading into the pharmacy. Been there.

Practicality aside - experts say there’s a critical public health reason why people should always wear their masks in the cold weather if they can’t distance properly.

It turns out that droplets that are exhaled behave differently in chilly, dry weather than they do in warm, humid weather. As a result, the risk of viral transmission during winter is greater than at any other time of year.

"Winter is a particularly dangerous time,” according to MUHC emergency room physician Mitch Shulman. “The virus likes cold, dry weather and so if you’re outdoors, not maintaining proper distancing, (or) wearing a mask, you are actually at more risk than you might otherwise have been.”

That’s in addition to the increased risk of transmission associated with spending much more time indoors during cold winter months, physically close to others and with little air circulation.

Outside, high levels of humidity in the air - or the lack of it, is what makes all the difference according to scientific theory, says infectious diseases specialist Dr. Earl Rubin.

“In the hot, humid air when you’re outside, the droplets, with the humidity drop faster,” said Rubin.

“The droplets that come out of your nose and mouth in cold air still drop but they drop slower and they stay afloat a little bit longer,” explained the Montreal Children’s Hospital expert.

And as the droplets hang in the air a little while longer, and as a conversation continues between maskless people on a frosty day - there is more opportunity for the virus that causes COVID-19 to infect others standing within two metres.

“You know when you breathe out in the winter you can see your breath? Imagine that’s literally what’s happening,” said Shulman,adding that there are only two solutions.

“You have to be even more careful in the winter about proper distancing when you’re outside and wearing a mask because the virus likes this weather,” the ER doctor concluded.

Rubin couldn’t agree more.

“I’ll never say don’t wear a mask. We don’t have very much in our tool kit to protect ourselves besides distancing, appropriate masking and good handwashing,” said Rubin, adding it’s a prudent thing to do regardless of the weather.

People are also more susceptible to all virus droplets in the winter for other reasons, according to University of Toronto epidemiologist Colin Furness, who spoke to Toronto news channel CP24.

The mucus membranes in our nose, mouth and throats also dry out in colder weather, he said, “and don’t work nearly as well at filtering out the pathogens.”

Being advised to wear a mask outside in winter to prevent COVID transmission might seem like a strange suggestion in Montreal, given all the blustery weather the city receives.

But Shulman said people may not realize that “for a breeze to protect you it has to be strong enough to blow out a match or a candle. Well, there isn’t always a lot of wind out there.”

It’s best to take protective measures into your own hands, the experts say - and put the mask on your face. 

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