According to the preprint, published last week, Sars-Cov-2 survives best at low temperatures in dry air. But even at warmer temperatures, droplets of the virus remain stable for far longer if the air lacks moisture (see chart).
Both findings will become increasingly relevant over the coming months.
During winter, as the air gets colder, it also dries out. But whacking on the heating indoors also reduces the amount of moisture in the air – as well as inside our sinuses. As mucus gets drier, it becomes worse at trapping infections in our airways.