In crisis situations, citizens’ situational awareness is paramount for effective response. While warning apps offer location-based alerts, their usage is relatively low. We propose a personalised messaging app channel as an alternative, presenting a warning bot that may lower adoption barriers. We employ the design science research process to define user requirements and iteratively evaluate and improve the bot’s usability and usefulness. The results showcase high usability, with over 40% expressing an interest in utilising such a warning channel, stressing as reasons the added value of proactive warnings for personalised locations while not requiring a separate app. The derived requirements and design solutions, such as graphically enhanced user interface elements as guardrails for effective and error-free communication, demonstrate that a suitable warning chatbot does not necessarily require complex language processing capabilities. Additionally, our findings facilitate further research on accessibility via conversational design in the realm of crisis warnings.