  The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, is
currently spreading rapidly throughout the world, causing many deaths and
severe economic damage. It is believed that hot and humid conditions do not
favor the novel coronavirus, yet this is still under debate due to many
uncertainties associated with the COVID-19 data. Here we propose surrogate data
tests to examine the preference of this virus to spread under different climate
conditions. We find that the disease is significantly (above the 95% confidence
level) more common when the temperature is $\sim$10$^\circ$C, the specific
humidity is $\sim$5 g/kg, and the ultraviolet (UV) radiation is $\sim$80
kJ/m$^2$. The significance of relative humidity is below the 95% confidence
level and does not show a preferred value. The results are supported using
global and regional data, spanning the time period from January to July 2020.
The COVID-19 data includes the daily reported new cases and daily death cases;
for both, the population size is either taken into account or ignored.
