It is often purported that unusually dry conditions provoke riots by intensifying the competition for water. The present paper explores this hypothesis, using data from Sub-Saharan Africa. We rely on monthly data at the cell level (0:5 0:5 degrees), an approach that is tailored to the fact that riots are short-lived and local events. Using a drought index to proxy for deviations of the actual climatic water balance from the normal one, we …nd that a one-standard-deviation fall in the index (signaling drier conditions) raises the likelihood of a riot in a given cell and month by 8.5 percent. We further observe that the e¤ect of unusual dryness is substantially larger in cells that combine a low supply of blue water with signi…cant agricultural activity, a …nding that supports the relevance of the water-competition mechanism.JEL classi…cation: D74, O13