 This study examined the seasonality of human social behavior in relation to respiratory disease transmission. It used a novel data stream on human mobility to characterize activity in indoor versus outdoor environments in the US. They found that the proportion of indoor to outdoor activity during a baseline year was seasonal, peaking in winter months. This measure also displayed a latitudinal gradient with stronger seasonality at northern latitudes and an additional summer peak in southern latitude. Additionally, they found that the disruption of the COVID-19 pandemic caused these patterns to shift significantly from baseline and the empirical patterns were necessary to predict spatiotemporal heterogeneity in disease dynamics. This article was authored by Zachary Suswin, Eva Searest and Shweta Bansal.