Knowing where to start reverse engineering a large software system, when no information other than the system?s source code itself is available, is a daunting task. Having the history of the code (i.e., the versions) could be of help if this would not imply analyzing a huge amount of data. In this paper we present an approach for identifying candidate classes for reverse engineering and reengineering efforts. Our solution is based on summarizing the changes in the evolution of object-oriented software systems by defining history measurements. Our approach, named Yesterday?s Weather, is an analysis based on the retrospective empirical observation that classes which changed the most in the recent past also suffer important changes in the near future. We apply this approach on two case studies and show how we can obtain an overview of the evolution of a system and pinpoint its classes that might change in the next versions.