Literature on agenda-building dynamics has neglected to assess the impact of contextual factors on the interplays between the issue attention of political actors and of the media. I fill the void by highlighting how media storms cause significant changes to the electoral communicational environment. Using a custom dataset compiled through an automated content analysis, I empirically examine patterns of issue salience during the 2015 Canadian federal election. The results support three main points. First, media storms do emerge during election campaigns. Second, media storms cause two main types of changes in the informational environment that characterize non-storm periods: (1) a reduction in the variety of issues included in the daily campaign coverage, and (2) a higher concentration of media attention on the storm-generating issues. Third, coverage of media storms compels political parties to engage with them, especially if they can exploit these storms with minimal risks. These findings suggest that some electoral contexts may be less conducive to political actors’ influence. They also offer evidence in support of the mediatization theory, according to which media market logic can take precedence over political normative logic in guiding the decisions of political actors.