Although dengue outbreaks cannot be prevented, it is possible to anticipate them. Scientists have recently identified a global climate indicator that may help improve predictions about the magnitude of dengue outbreaks several months in advance. This indicator, which can be used for any world region, is based on temperature fluctuations at the surface of the Indian Ocean. Obtaining reliable long-term predictions could facilitate efforts to tackle this infection, which has been on the rise for several decades and threatens half of the world's population.