Before revision:  Statistical analysis is performed to assess the relationship between the transmissibility of COVID-19 and the temperature/humidity,by controlling for various demographic, socio-economic, geographic, healthcare and policy factors and correcting for cross-sectional correlation. We find a similar influence of the temperature and relative humidity on  effective reproductive number (R values)of COVID-19 for both China and the U.S. before lockdown in both countries: one-degree Celsius increase in temperature reduces R value by about 0.023 ( 0.026 (95\% CI [-0.0395,-0.0125]) in China and  0.020 (95\% CI [-0.0311, -
After revision:  Participants: A total of 69,498 cases in China and 740,843 cases in the U.S. are used for calculating the effective reproductive numbers. Primary outcome measures: Regression analysis of the impact of temperature and relative humidity on effective reproductive number (R values)of COVID-19 for both China and the U.S. before lockdown in both countries: one-degree Celsius increase in temperature reduces R value by about 0.023 ( 0.026 (95\% CI [-0.0395,-0.0125]) in China and 0.020 (95\% CI [-0.0311, -