Altimetric rain-flagging, based on the expected relationship between radar backscattering at Ku- and C-band, was developed two decades ago and has become part of the operational quality control. However, a number of other conditions such as wave height and sea surface temperature (SST) also modulate the values of sigma0, and thus affect the mean relationship between the backscatter values at these two frequencies In this work I quantify the effects of significant wave height and SST for both the Jason-2 and Jason-3 altimeters, and assess the improvements in the retrieval of rain rate. An assessment will also be given of the sigma0 values returned by the Sentinel-3 altimeter, when it is operating in its delay-Doppler mode.