Alan Barreca in The Weather Channel — Coronavirus and the Seasons: What We Know and Don’t Know

As the novel coronavirus wreaks havoc on societies and economies around the world, many are wondering if the return of summer might put a crimp in the virus’s spread across northern countries, including the United States. There’s a substantial body of research showing that influenza tends to peak in the cold season and wane in the summer across midlatitudes. The key meteorological factor isn’t the heat – it’s the humidity. More recent work, including research led by Alan Barreca (University of California, Los Angeles), show that absolute humidity – the total amount of water vapor in the air – is a particularly useful index. In a 2017 study, Barreca and colleagues found that incorporating absolute humidity leads to a 3-5% improvement in forecast accuracy for models of flu transmission extending out to 4 weeks.