The inter-annual variability of East African March-April-May (MAM, “long rains”) precipitation and the processes responsible for the recent drying trend are examined using global model simulations and analysis of observations. The differences between a control and a series of re-initialized simulations where variability due to land-surface feedbacks is suppressed show that much of the decline in “long rains” experienced over the period between 1980 and 2014 is associated with the warming of northwestern Asian land mass. In agreement with the modeling results, analysis of multiple observational datasets indicate strong correlation between MAM mean East African rainfall amount and the land surface temperature over northwestern Asia. Further analysis of idealized simulations indicates that warming northwestern Asia introduces subsidence that favors transport of moisture poleward away from the region.