Where You Sit Matters More Than Where You Play: Systemic Thermal Exposure Inequality Across the 2026 FIFA World Cup

Abstract Geographically distributed mega-sporting events create systemic variations in spectator thermal exposure that traditional venue-level risk assessments fail to capture. Adopting a system-level perspective, this study investigates whether ambient thermal exposure emerges as a property of tournament design by quantifying inter-venue thermal exposure heterogeneity at the 2026 FIFA World Cup using surface weather observations and spectator-weighted exposure metrics. Our findings show that thermal risk was a structural property of tournament design, with inter-venue spatial variance dominating intra-venue temporal variability. Geographic venue assignment accounted for 71% of the variance in ambient Wet-Bulb Globe Temperature (WBGT), generating a 12.5°C disparity between the hottest and coolest host cities. This inequality translated into a highly asymmetric population-level health risk: 95% of the cumulative thermal burden (spectator-degree-hours above 28°C) was concentrated in just three venues—a concentration that remained robust across thresholds (85% at 26°C, 100% at 30°C; Table 4). Our analyses identify match scheduling as the primary modifiable driver of within-venue exposure, while validation against ERA5 reanalysis reveals that global models systematically underestimate aggregate thermal exposure at the venue level, with individual match classifications near risk thresholds remaining sensitive to methodological assumptions—reinforcing the operational case for complementing reanalysis with local station data. Future spectator heat management therefore depends not only on forecasting weather, but on understanding how tournament design distributes thermal exposure across populations.