The Role of Weather Conditions in COVID-19 Transmission: A Study of a Global Panel of 1236 Regions

Zhang, C.; Liao, H.; Strol, E.; Li, H.; Li, R.; Jensen, S. S.; Zhang, Y.

Weather condition may impact COVID-19 transmission. The effects of temperature and humidity on COVID-19 transmission are not clear due to the difficulties in separating impacts of social distancing. We collected COVID-19 data and social-economic features of 1236 regions in the world (1112 regions at the provincial level and 124 countries with small land area). Moreover, a large-scale satellite data was combined with these data with a regression analysis model to explore effects of temperature and relative humidity on COVID-19 spreading, as well as the possible transmission risk due to temperature change driven by seasonal cycles. The result showed every degree Celsius increase in average temperature appears to cause a 2.88% decrease in the fraction of new daily cases 6 days later and a 0.62 percent point decrease in the reproductive number (R0). Every percentage point increase in relative humidity is found to lead to a 0.19% decrease in the fraction of new daily cases and a 0.02 percent point decrease in R0 6 days later. Further, the effect of temperature and humidity is near to linear based on our samples. Government intervention (e.g. lockdown policies) and lower population movement contributed to the decrease the new daily case ratio. The conclusions withstand several robustness checks, such as observation scales and maximum/minimum temperature. The conclusion indicates air temperature and relative humidity are shown to be negatively correlated with COVID-19 transmission throughout the world. Given the diversity in both climate and social-economic conditions, the risk of transmission varies globally and possibly amplifies existing global health inequalities. Weather conditions are not the decisive factor in COVID-19 transmission, in that government intervention as well as public awareness, could contribute to the mitigation of the spreading of the virus.