A large lecture introductory course at Iowa State University has used a forecasting activity since 1993 to actively engage students in doing science. This automatically scored Web-based activity requires students to evaluate selected weather parameters and to also select appropriate physical reasons for their values. Participants can select from more than 1000 cities in the United States for their forecast city. This activity engages students in doing what practicing meteorologists do. Further, forecast scores demonstrate increased understanding throughout the course. Design considerations were based on constructivist learning theory in order to address goals articulated by national panels; to promote problem solving, collaboration, and communication skills by being involved in scientific inquiry.