We present a study using a mobile AR (Augmented Reality) App to enhance large lecture classes both inside and outside the classroom. When students scan the target images using the App as directed by the instructor during the class, animated instructive materials, such as different cloud formation, are presented directly on individual students’ mobile screens. When students study independently outside the classroom, audio instruction and sound effects features of the App can be used along with the visual presentation. Unity and Vuforia were used for the cross-platform (iOS and Android) development of the App. The App was deployed and tested in an Introductory Meteorology class through in-class instructor led demo and students independent usage outside classroom. A survey was administered to collect feedback on students’ attitudes, engagement and satisfaction level, app performance, and other learning and user experiences toward the App. Responses from 95 students were received and analyzed. The survey results indicate that majority students have found the App to be engaging, satisfactory, and considered it to be a promising learning tool. Through the study, AR mobile App is shown to have great potential to be utilized as an active learning tool in large lecture class settings where it’s difficult for instructors to engage with individual students.