What are the effects of climate variables on COVID-19 pandemic? A systematic review and current update

The climatological parameters can be different in various geographical locations. Moreover, they have possible impacts on COVID‑19 incidence. Therefore, the purpose of this systematic review article was to describe the effects of climatic variables on COVID‑19 pandemic in different countries. Systematic literature search was performed in Scopus, ISI Web of Science, and PubMed databases using (“Climate” OR “Climate Change” OR “Global Warming” OR “Global Climate Change” OR “Meteorological Parameters” OR “Temperature” OR “Precipitation” OR “Relative Humidity” OR “Wind Speed” OR “Sunshine” OR “Climate Extremes” OR “Weather Extremes”) AND (“COVID” OR “Coronavirus disease 2019” OR “COVID‑19” OR “SARS‑CoV‑2” OR “Novel Coronavirus”) keywords. From 5229 articles, 424 were screened and 149 were selected for further analysis. The relationship between meteorological parameters is variable in different geographical locations. The results indicate that among the climatic indicators, the temperature is the most significant factor that influences on COVID‑19 pandemic in most countries. Some studies were proved that warm and wet climates can decrease COVID‑19 incidence; however, the other studies represented that warm location can be a high risk of COVID‑19 incidence. It could be suggested that all climate variables such as temperature, humidity, rainfall, precipitation, solar radiation, ultraviolet index, and wind speed could cause spread of COVID‑19. Thus, it is recommended that future studies will survey the role of all meteorological variables and interaction between them on COVID‑19 spread in specific small areas such as cities of each country and comparison between them.