The unique coronavirus (SARS-CoV-2) has spread around the world, prompting the World Health Organization to proclaim a pandemic. While influenza viruses have a seasonal pattern, it is unknown if COVID-19 is affected by the weather. In this paper, we look at the weather patterns in all of the COVID-19-affected regions around the world. Our findings show that between 3 and 17 °C, and 1 and 9 g/m3, roughly 85 percent of COVID-19 reported cases (out of approximately 29 million tests completed) occurred in places with temperatures between 3 and 17 °C and absolute humidity between 1 and 9 g/m3. Similarly, outside of these limits, hot and humid locations have only reported about 15% of cases, or about 0.5 million cases (out of approximately 7 million tests performed). This implies that COVID19's global spreading could be influenced by the weather. However, in US and European cities (above 45 N), this role may be limited because mean temperature and absolute humidity levels may not approach these levels even during the peak summer months. Since the beginning of March, most hot and humid countries have been experiencing temperatures >35 °C and absolute humidity >9 g/m3, and thus the effect of weather, however minor, has already been accounted for in the COVID-19 spread in those regions, and they must take strict social distancing measures to prevent COVID-19 from spreading further. Our research found that the effect of weather may have only slowed the spread of COVID-19.
