The link between extreme weather and climate change is being highlighted in ever more countries. Increased public understanding of this issue is essential for policymaking, both in terms of climate change mitigation and adaptation. As social media are becoming central to the exchange of information in society, the purpose is to analyze what generates intensified attention to the connection between extreme weather and climate change in digital communication. This is done by examining periods of intensified co-occurrence of mentions of extreme weather and climate change on English-language Twitter (N = 948,993). Our quantitative analysis suggests that during the period 2008–2017 the years 2010, 2011 and 2017 exhibit a considerable increase in ‘causality discourse’, i.e. tweets that articulate the topic of climate change + extreme weather, in comparison with earlier years. These periods of significant growth are interpreted as involving dynamic relationships between three factors, namely mediated highlighting of previous or ongoing extreme-weather events (extreme-event factor); connection of extreme weather to climate change by traditional media or other intermediaries (media-driven science communication factor); and actions of individual users (digital-action factor). Through a qualitative discourse analysis, how these factors jointly generate increasing attention to ‘causality discourse’ is more closely explored for the case of 2017.