AbstractPrevious studies emphasized the role of transient disturbances in linking interannual variation of average rainfall (IVAR; average period > 1 month) to external climate forcings. Researchers conventionally use transient eddy‐driven horizontal fluxes of certain variables to explain the IVAR, which is not universally applicable to disturbance‐associated IVAR research because these variables' horizontal distributions can drastically affect their fluxes. Here we demonstrate that the strengthened transient disturbance activities can directly impact IVAR positively in almost all extratropical terrestrial regions in each season. This impact occurs because disturbance strengthened daily downward motions cannot generate negative rainfall to compensate for the increased rainfall generated by disturbance enhanced daily upward motions. This is much more universally applicable to disturbance‐associated IVAR research because it derives transient eddies' direct and independent impacts on IVAR. Because of this impact, the horizontal heterogeneity of global warming rate can modify the long‐term trend of extratropical terrestrial rainfall through disturbance activity trend.