The human impacts on the climate through emissions of greenhouse gases and aerosols, as well as land use changes, are widely recognized. However, to what extent mass human migration can affect the climate remains largely unknown. The population movements around the Chinese New Year (CNY) represent the world's largest annual human migration. In the present study, we investigate the role of mass human migration in influencing the urban heat island (UHI) during the CNY holiday for the period 2005-2013 in Zhengzhou city, a typical large city in central China. It is found that the UHI effects expressed as daily mean (ΔT_mean), maximum (ΔT_max), and minimum (ΔT_min) surface air temperature differences between the stations of Zhengzhou and Zhongmou, averaged over the period 2005-2013 during the CNY week, are 0.16℃, 0.29℃ and -0.03℃, respectively; and these values are 0.50℃ (76%), 0.06℃ (16%) and 0.66℃ (105%) lower than those during the background period (2-4 weeks before the CNY week and after the CNY week), respectively. Changes in ΔT_mean and ΔT_min are both significant at the 99% confidence level by the Student's t-test.