Analysis in 27 cities across China shows that surface solar irradiance (SSI) and wind speed track similar decadal trends in 1961–2011, suggesting wind speed as a possible regulator of SSI. This assumption is further confirmed by the continuously widening gap in annually averaged daily SSI between windy and windless clear-sky days with worsening air pollution. Wider gaps are noted for more polluted cities and seasons. The gap in SSI between windy and windless conditions could therefore serve as a good indicator for air quality. The regulatory effect of wind speed on SSI starts to be important when air pollution index exceeds the boundary of 125. A plausible mechanism of wind speed regulating SSI through interactions with aerosols is proposed. There are two cut-off points of 2.5 m s？1 and 3.5 m s？1 wind speeds. Winds <2.5 m s？1 noticeably disperse air pollutants and thereby enhance SSI. Above the 2.5 m s？1 threshold, air pollution and SSI become largely insensitive to changing wind speeds. Winds in excess of 3.5 m s？1 could enhance aerosol concentration probably by inducing dust-storms, which in turn attenuate SSI.