Will COVID-19 be worse in winter?

Common cold coronaviruses have been found wherever scientists have looked, regardless of season. However, in temperate climate zones (most of the Continental US), the common cold coronavirus and seasonal influenza infections typically peak in winter. Why do these viruses show seasonality?  

One reason is that cooler, drier environments are associated with longer viral stability and smaller aerosol size. This is true for both influenza and coronaviruses. Thus the viruses can stay suspended in the air for longer, giving them a higher chance of infecting people. 

Another reason is that cool, dry air also means your body is slower to clear pathogens from your nose. Plus, your mucous (snot)--which usually protects you from infections-- changes with the winter weather and doesn’t work as well.

We do not have enough data yet to fully understand how COVID-19 will behave. But a small study from Australia looked at local COVID cases in March, 2020, in relation to temperature and humidity. They found a reduction in relative humidity of 1% was associated with an increase in COVID-19 cases of 6%. 

With more time spent indoors and reopening schools, there is potential for a resurgence of COVID. Unfortunately, we’ll only know for sure once we’re there. In any case, social distancing, washing your hands, and wearing a mask will remain helpful ways to reduce your risk.


Last update: Aug 28, 2020 1:56 pm ET

Science review: GSN, ERS, JAB