The seasonality of influenza led to speculation that the coronavirus could be similarly susceptible to the onset of warmer weather. Early research and the strength of initial outbreaks in some warm climates suggested that any such effect would be at best offset by other factors. The World Health Organization advised that the virus could be transmitted "in any climate."
In May, a Harvard "working paper" found that warmer temperatures and moderate sunlight exposure might slightly offset the rate of infection spread, but predicted "upcoming changes in weather alone will NOT be enough to fully contain the transmission of COVID-19."
Similarly, the National Institute of Health found that "summer weather will not substantially limit pandemic growth" until more of the population was resistant to the virus.