Spatiotemporal characteristics of urban dry/wet islands in China following rapid urbanization

•Temporal and spatial variation of dry/wet islands in urban areas at national scale.•Absolute humidity is increasing with rise of urban artificial water dissipation.•Cold and dry cities are prone to be wet islands, while humid ones to be dry islands.•Most of the cities are prone to be dry islands in summer, while wet in winter.•Absolute humidity of all cities increased in winter after urbanization.