Surface humidity in Shanghai has changed over the past 49 years, with the highest levels in the 1990s and the lowest in the 1960s. Summer humidity has increased while autumn humidity has decreased. The southern part of Shanghai generally has higher humidity than the northern part. The increase in humidity is influenced by precipitation and potential evapotranspiration. When precipitation increases more than potential evapotranspiration, humidity increases, and vice versa. Factors like sunshine duration and temperature also affect humidity levels. More research is needed to accurately assess humidity in urban areas.