Heat-related illness prevention measures at summer mass gathering rock festivals: A comparative analysis of 2023 and 2024 in Japan

Summer mass gathering rock festivals are increasingly conducted in extreme heat, posing a substantial risk of heat-related illness. In Japan, several major rock festivals in 2023 experienced wet bulb globe temperature (WBGT) levels classified as “Danger” or “Severe Warning,” raising concerns about preventive measures and on-site preparedness. Building on these findings, this study conducted a comparative descriptive analysis of environmental heat risk indicators and heat-related illness mitigation strategies at four major outdoor rock festivals in Japan during the summers of 2023 and 2024. Daily maximum WBGT values and the timing of peak WBGT were obtained from the meteorological observation stations closest to each venue and preventive measures implemented by festival organizers were systematically reviewed using publicly available information. Across both years, all festivals were conducted under high heat-risk conditions, with daily maximum WBGT values reaching the “Danger” or “Severe Warning” levels and peak WBGT consistently observed around midday. Despite sustained environmental risks, several improvements in mitigation strategies were identified in 2024, including expanded permission for sports drink carry-in, increased allowance for parasol use at outdoor stages, and an increased number of on-site first-aid stations at selected festivals. These results indicate that, although extreme heat remains a persistent challenge at summer rock festivals, adaptive improvements in mitigation measures can be implemented over time, underscoring the value of systematically monitoring heat risk indicators and establishing preventive practices for mass gathering preparedness under a warming climate.