There is growing evidence that climatic factors could influence the
evolution of the current COVID-19 pandemic. Here, we build on this
evidence base, focusing on the southern hemisphere summer and autumn
period. The relationship between climatic factors and COVID-19 cases in
New South Wales, Australia was investigated during both the exponential
and declining phases of the epidemic in 2020, and in different regions.
Increased relative humidity was associated with decreased cases in both
epidemic phases, and a consistent negative relationship was found
between relative humidity and cases. Overall, a decrease in relative
humidity of 1% was associated with an increase in cases of 7-8%.
Overall, we found no relationship with between cases and temperature,
rainfall or wind speed. Information generated in this study confirms
humidity as a driver of SARS-CoV-2 transmission.