In this article, the author describes the "Be your own groundhog" project in her grades 9-12 Earth and environmental sciences courses, in which students use citizen science databases to research the physical changes that signal the arrival of spring. This project starts with a simple question, "When will spring spring?" This goes beyond the astronomical date of the vernal equinox to terrestrial meanings of spring--warmth, flowers, migrations. By using the observational science of phenology and data sets contributed by citizen scientists and available online, students create and refine predictive models, demonstrating the science practices described in the "Framework." Even those students who previously avoided science find this activity engaging and interesting, which is why it will remain a part of the author's curriculum for years to come. (Contains 3 figures and 5 online resources.)