Corresponding observational data of daily air temperature and dew-point temperature were obtained from the Weather Underground website (https://www.wunderground.com/). The relative humidity and the absolute humidity were calculated using daily air temperature and dew-point temperature. Maximum/minimum temperatures and temperature difference on each day were also calculated for each state/country. Furthermore, time-series of zonal mean temperature at 1000 mb in 2019 was calculated from National Centers for Environmental Prediction reanalysis data to study the trend of approximate global COVID-19 dispersal.