Along with the bright hues of orange, red, and yellow, the season of fall represents significant changes, such as day length and temperature. These changes provide excellent opportunities for students to use science process skills to examine how abiotic factors such as weather and temperature impact organisms. In this article, the authors describe an activity that uses available Internet data to encourage students to explore the relationship between seasonal patterns and climate (plant phenology) as well as day-length data. In particular, students develop and test hypotheses to explain latitudinal differences in leaf-color change. The activity allows students to see that some questions cannot be answered immediately without long-term data. At the same time, the activity allows students to ask questions and obtain long-term data quickly to assist them in developing and evaluating hypotheses. (Contains 6 figures and 5 resources.)