Media Framing of Heatwaves in Japan: Misalignment between Temperature and News Coverage

This study examines how Japanese news media frame high-temperature days as heatwave events, investigating potential discrepancies between meteorological standards and media representations. We analyzed 2,766,793 articles from Yahoo! News Japan to identify when news agencies significantly increased their heatwave coverage, using Kleinberg’s burst detection algorithm to identify "heatwave days" in media discourse. Employing gradient boosting models, we analyzed the relationship between population-weighted temperatures and media coverage patterns across Japan. Our findings reveal that media outlets consistently use a lower temperature threshold (approximately 30°C) than the Japan Meteorological Agency’s official criterion of 35°C when framing heat events as heatwaves. We identified both "overreacted" cases, where moderate temperatures received disproportionate coverage, and "overlooked" cases, where high temperatures went unreported as heatwaves. Content analysis of articles published during these misaligned periods shows that overreacted coverage typically functioned as early warnings for approaching heat events, while overlooked cases reflected attention fatigue during extended high-temperature periods. These results illuminate how media integrate meteorological phenomena with public health discourse, offering insights for improving climate change communication and understanding the interplay between scientific measurement and social construction of extreme weather events.