Classroom emotional climates (ECs) are interrelated with students' engagement with university courses. Despite growing interest in emotions and EC research, little is known about the ways in which social interactions and different subject matter mediate ECs in preservice science teacher education classes. In this study we investigated the EC and associated classroom interactions in a preservice science teacher education class. We were interested in the ways in which salient classroom interactions were related to the EC during lessons centered on debates about science-based issues (e.g., nuclear energy alternatives). Participants used audience response technology to indicate their perceptions of the EC. Analysis of conversation for salient video clips and analysis of non-verbal conduct (acoustic parameters, body movements, and facial expressions) supplemented EC data. One key contribution that this study makes to preservice science teacher education is to identify the micro-processes of successful and unsuccessful class interactions that were associated with positive and neutral EC. The structure of these interactions can inform the practice of other science educators who wish to produce positive ECs in their classes. The study also extends and explicates the construct of "intensity of EC."