Warmer weather unlikely to reduce the COVID-19 transmission: An ecological study in 202 locations in 8 countries

PURPOSE: To examine the association between meteorological factors (temperature, relative humidity, wind speed, and UV radiation) and transmission capacity of COVID-19. METHODS: We collected daily numbers of COVID-19 cases in 202 locations in 8 countries. We matched meteorological data from the NOAA National Centers for Environmental Information. We used a time-frequency approach to examine the possible association between meteorological conditions and basic reproductive number (R(0)) of COVID-19. We determined the correlations between meteorological factors and R(0) of COVID-19 using multiple linear regression models and meta-analysis. We further validated our results using a susceptible-exposed-infectious-recovered (SEIR) metapopulation model to simulate the changes of daily cases of COVID-19 in China under different temperatures and relative humidity conditions. PRINCIPAL RESULTS: Temperature did not exhibit significant association with R(0) of COVID-19 (meta p = 0.446). Also, relative humidity (meta p = 0.215), wind speed (meta p = 0.986), and ultraviolet (UV) radiation (meta p = 0.491) were not significantly associated with R(0) either. The SEIR model in China showed that with a wide range of meteorological conditions, the number of COVID-19 confirmed cases would not change substantially. CONCLUSIONS: Meteorological conditions did not have statistically significant associations with the R(0) of COVID-19. Warmer weather alone seems unlikely to reduce the COVID-19 transmission.