It has been long recognized that cloud‐free regions are typically associated with drier air, whereas cloudy regions typically are associated with more moisture. Using Advanced Microwave Scanning Radiometer (AMSR‐E) passive microwave observations, we estimated the bias between water vapor path (WVP) of clear‐sky and all‐sky conditions. Furthermore, we assessed the impact of these biases on longwave cloud radiative forcing (CRF). Results indicate that, in a zonal mean sense, the difference between all‐sky and clear‐sky WVP estimates is around 2 mm, with highest values in the midlatitudes summer, where differences up to 7 mm occur. The corresponding CRF change forced by these WVP changes is about 2 W m−2 in a zonal mean sense. Highest values occur in the midlatitudes of the northern hemisphere in which a magnitude up to 6 W m−2 is shown. Over the convectively active regions, the WVP contributed CRF appears to be smaller than 5 W m−2, substantially smaller than the CRF contributed by upper tropospheric water vapor only, suggesting that a significant portion of satellite‐estimated CRF over the tropics is contributed by the redistribution of water vapor associated with convection development.