ENSO SST variability follows a seasonal pattern, with warmer temperatures in the eastern Pacific leading to deeper clouds in the beginning of the year. These clouds have a negative feedback effect on surface radiation, contributing to the observed seasonal phase-locking of ENSO. Both observations and model simulations show that this relationship is crucial in understanding the predictability of ENSO. The study highlights the importance of seasonally changing cloud feedbacks in influencing ENSO variability.