Covid-19 and the Weather

Everybody’s probably heard that it appears that summer weather will impede the spread of the virus and that, in general, the virus prefers cooler and drier weather. As the article below makes clear, the dryness of the air seems to be more central than the coolness. Also, it is worth pointing out that in many parts of the country, a large percentage of the population spends the bulk of their summer hours in a group environment of cool, dry, recirculated air.

The research suggests that a relative humidity of 40 percent to 60 percent could help the body fight off the virus.

If you live in a dry climate or are experiencing unusually dry weather but don’t have a humidifier (and circumstances don’t really justify buying one), an old trick you can use in a pinch is get a spaghetti pot simmering on the stove with a vented lid on it. You can easily get the humidity in a smallish apartment (about 600 square feet) to stabilize between 40 and 60% using this method. One thing to be on the lookout for is how this affects your pots and pans. The water in San Diego appears to be on the alkaline side, which results in a calcified residue accumulating on the lower interior sides of the pot if you leave it simmering for hours. However, I discovered for unrelated reasons that putting a little bit of vinegar in the water not only prevents this but can also be used to “clean” any alkaline residue that has accumulated in the past.

Retrieved from Newsweek at

This characteristic of the virus offers hope that we can mitigate the spread of the novel coronavirus with simple measures such as installing humidifiers in the home. In the dry winter months, cold air gets pulled into the home and heated, which lowers the relative humidity—in other words, the heated air is capable of holding more moisture than it actually contains. Such dry air impairs the lungs’ ability to clear out invading viruses and the immune system’s ability to keep the virus from replicating. “We spend 90 percent of our lives indoors, where the air is very dry in the winter,” says Akiko Iwasaki, a Yale immunobiologist who led one of the studies, with Hugentobler as a co-author. “That’s exactly when the virus best survives and transmits.”


Around the time Iwasaki’s study was posted, MIT’s Rahmandad was pondering the variation in COVID-19 infection rates throughout Iran’s provinces. He noticed that the warmer, more humid parts of the country seemed less affected by the disease—as was much of warm-and-humid India and the rest of South Asia, even though the high population density and traffic with China should have made those areas ideal for fast spread of infections. “It all suggested that something related to the weather was important,” says Rahmandad.