Abstract: The humidity index was selected to study changes in dry and wet climates across four major climate regions in China from 1960 to 2019. Using the partial differential equation method, the specific contributions of major climate factors to variations in the humidity index were quantified. In the past 60 years, among which different climate regions exhibited varied trends; namely, the arid region of China showed a significant trend toward humidification, most semi-arid and semi-humid regions exhibited a drying trend, and most humid regions became wetter. The dominant driving factors of dry and wet changes varied significantly across different climate regions. The significant increase in precipitation (accounting for 54.3% of the changes in dry and wet conditions) led to climate wetting in the arid region. Meanwhile, in the semi-arid region, the significant increase in average temperature (accounting for −35.4% of the changes in climatic conditions) dominated climate drying. In the semi-humid region, the decrease in precipitation and relative humidity (accounting for −45.4%) dominated the drying trend. The increase in precipitation (accounting for 34.0%) and the decrease in net radiation (accounting for 31.2%) led to climate humidification in the humid region. Furthermore, in semi-arid and sub-humid regions, factors related to potential evapotranspiration, such as net radiation, average temperature, and relative humidity, contributed more significantly to changes in dry and wet conditions than precipitation.