Political action in reponse to the COVID-19 crisis generated hope for political action on a larger looming crisis, the climate crisis. Articulating climate change in terms of crisis and positioning it in the context of apocalypse can be an effective mobilizer of short-term action. Yet, alarmist discourse risk plunging people into apathy. In this article, we examine imaginaries of the climate crisis invoked by climate activist organizations during the COVID-19 pandemic, as they tried to influence the political agenda on Twitter (now X) and, not least, call for action on the climate crisis. We identify five key activist climate imaginaries and show how an apocalyptic imagery was invoked in response to the pandemic. However, this apocalyptic imaginary was rarely invoked on its own, but in relation to other key climate imaginaries. Our findings contribute to research on agenda setting and the role of political imaginaries in struggles over societal transformations, and especially the role of activist imaginaries when challenging dominant climate imaginaries in attempts to influence the political agenda and generate political action.