AbstractCitizen-government communication is essential in preparedness and adaptation to climate events. Local-level government authorities have sought to communicate via social media, but little is known about their communication strategies and citizens’ participation in replying to their publications. This study draws on conceptual frameworks for Social Media Presence and Human Engagement to establish behavioural modelling and topic modelling approaches for assessing citizen-authority communication from a long-term perspective. Empirical analyses focus on official government authorities for the Brazilian cities of São Paulo, Rio de Janeiro, Belo Horizonte, Porto Alegre and Belém, which cover over 25 million people and 500 thousand followers on the X platform (former Twitter). Analyses are based on 10.2 thousand authorities’ publications and their 5.5 thousand received replies from 2.6 thousand people over one year. Findings show that authorities use periodic passive posting, providing meteorological, hydrological, and geological alerts, forecasts, and momentary weather updates. Citizen engagement is short-term, providing corrections, additions, and updates but not connecting weather events with climate change. Practice-oriented implications concern the adequacy of social media for providing citizens awareness, keeping them updated, and building their trust in authorities over climate event developments.