A semi-quantitative and dynamic scenario is proposed for a dry climatic phase during the late Quaternary of central Amazonia. This scenario has been developed on the basis of previous studies by different authors, augmented by results of several months of field work, by using the present climate as a comparison system. The main features of that probable climate are: a general savanna vegetation nature; a strong seasonality in precipitation; annual precipitation of the order of 850–1000 mm; general circulation systems similar to the present ones; regional atmospheric systems were very weak; wet season from November to April; a dry season from May to October; a 10-fold variation in river discharge and seasonal oscillations of about 12 m (i.e. double the present value) at Obidos; minor tributaries with intermittent regime and arroyo/alluvial dynamics; trade winds stronger and drier than the present ones; little recycling of local waters in precipitation. Two unexpected conclusions became apparent. (1) The excess of humidity in the present climate of central Amazonia is not as high as it appears at first glance. (2) No more than second-order changes in the regional dynamics are needed for the occurrence of a dry climatic phase.