As teachers of first-year college mathematics and science students, the authors are constantly on the lookout for simple classroom exercises that improve their students' analytical and computational skills. In this article, the authors outline a project entitled "Predicting Precipitation in Darwin." In this project, students: (1) analyze and manipulate raw precipitation data; (2) build a prediction model using a Markov chain; (3) predict the long term distribution of precipitation-free and rainy days in Darwin, Northern Territory, Australia; (4) use a chi-square test to evaluate the effectiveness of the model they have constructed; and (5) improve their prediction model. Beyond access to the Internet (to obtain the raw data) and a computer spreadsheet program or calculator, no special equipment is required. If the data is downloaded in advance, a well-prepared junior or senior high-school mathematics (or science) class should be able to perform this exercise in approximately 30-45 minutes of class time. (Contains 1 figure and 8 tables.)