Whilst social distancing (e.g., during a pandemic), electronic communication allows users to keep in touch with social contacts, thereby fulfilling needs for human interaction. Accordingly, it is important to examine social closeness in the context of computer-mediated communication in more detail and to take a closer look at the relation between the feeling of presence to achieve the maximum potential for such communication. In this paper we introduce the concept of sensory synchronization as a predictor for perceived social presence. To this end, social activities conducted virtually during the Covid-19 pandemic were surveyed and analyzed to understand the connection between a feeling of presence and possible sensory synchronization of communication partners. Context of activities were collected in preliminary interviews and examined more closely in an online survey (N = 234). Most frequently reported activities included video calls, playing virtual games and virtual meals. The results showed that there is a significant positive correlation between sensory synchronization and social presence in all activity categories. The activity categories significantly explain different variances of the evaluated social presence and sensory synchronization. The results of this work motivate further research on the topic of sensory synchronization and social presence. New predictors in social presence research were identified and a questionnaire for the assessment of sensory synchronization and social presence was developed.