Social networks such as Twitter enable people to interact with each other and share health-related concerns in an effective and novel way, as evidenced during the COVID-19 pandemic when in-person communication became inconvenient under social-distancing policies. Public emotions mined from these social network data have increasingly attracted scholars’ attention because of their significant role in predicting public behaviors. However, little attention has been paid to the impacts of health policy and local political ideology on the trends of spatiotemporal emotions related to COVID-19. This study examines 1) the spatial-temporal clustering trends of negative emotions (or spillover effects); 2) whether health policies such as social distancing policy are associated with spatiotemporal emotion patterns towards COVID-19. This article finds that: COVID-19 related negative emotions detected by social media have spillover effects and that counties with stay-at-home policy or counties that are predominantly democratic exhibit a higher observed number of negative emotions toward COVID-19. These results suggest that scholars and policymakers may want to consider the impacts of interventions caused by public policy and political polarization on spatial-temporal patterns of public health concerns detected by social media.