The impact of weather on the spread of COVID-19. The case of the two largest cities in Greece

The new global pandemic of COVID-19 declared on March 11, 2020, by the World Health Organization, has already had an unprecedented impact on health and socioeconomic activities worldwide. The second wave of the COVID-19 pandemic swept through the United States of America and Europe in late September 2020. Compared with other southern countries, such as Greece, where there was a significant increase in cases at the end of October 2020, Northern European countries (Germany, France, Austria, Finland, and Sweden) experienced this second wave of the pandemic earlier in September 2020. To understand the epidemiological behavior of the virus in Greece, from an environmental point of view, we examined the effects of air temperature, humidity, and wind on the spread of COVID-19. More specifically, we studied whether hot and humid conditions are associated with a decrease in epidemiological indicators of the pandemic and whether cold and dry conditions are associated with an increase in these indicators and therefore contribute positively to the spread of COVID-19. We applied Pearson correlation analysis and generalized linear models (GLM) with confirmed admissions to intensive care units (ICU) with COVID-19 from the National Public Health Organization, as dependent variables and the corresponding air temperature, humidity, and wind speed from the Greek National Meteorological Service, as independent covariates. The analysis concerns Athens and Thessaloniki, the two largest cities in Greece.