A well-designed science investigation that has students examine and graph seasonal temperature data from cities at different latitudes. They describe trends they see, and explain what they think causes these trends. They then identify the likely factors causing the seasonal trends, and choose one that they develop a hypothesis for. This is investigated using data from the US Naval Observatory, and the findings are written up in scientific format and communicated to the class. A final assignment involves explaining in writing what the reasons for the seasons are. An extensive student handout is provided.