Flu Weather: It's Not the Cold, It's the Humidity
Bob Henson · February 9, 2018, 11:47 AM EST
Folk wisdom has it that cold weather predisposes you to a cold or flu bug. The truth is a bit more complicated—and a lot more interesting. Research over the past few years has zeroed in on atmospheric moisture as the main weather-related factor in flu transmission. The findings are especially relevant this winter, with the U.S. in the throes of one of its worst winters of flu in years, and its driest winter in more than three decades.
The key seems to be humidity levels inside, where people gather (and cough) during cold weather. Because it takes less moisture to saturate cold air than warm air, there can easily be high relative humidity (RH) outside on a bitterly cold day. However, once that air is heated to room temperature, the RH plummets.
https://www.wunderground.com/cat6/flu-weather-its-not-cold-its-humidity
