Deforestation of the entire Amazon basin - the catastrophe scenario - is projected to result in regional decreases of precipitation and evaporation, potentially leading to sustained desertification. However, current levels and patterns of Amazon deforestation actually enhance mass and energy transfers between the land and the atmosphere through the creation of thermally driven circulations. The climatological effects of these circulations have long been thought to be inconsequential (e.g., Negri et al., 2004). In contrast, we find here that current deforestation causes a dramatic change in climatological rainfall occurrence patterns; high-resolution satellite precipitation measurements show significantly more rainfall occurrences (p ≤ 0.0001) over deforested areas. Moreover, a 75 year-long rain gauge record shows a long-term shift in the seasonality of precipitation that is concurrent with deforestation. These findings suggest that current deforestation in the Amazon has already altered the regional climate. Such changes have implications for regional ecosystem dynamics, but may also affect global climatic patterns through tropospheric teleconnections.