A recent study by Insee highlights the disparity in heat exposure among socioeconomic groups in nine French metropolitan areas. Lyon showed the largest temperature gap during summer 2017, with a notable 0.41°C difference between wealthiest and poorest households. These urban heat islands—exacerbated by concrete, vehicular traffic, and air conditioning—pose a higher risk to vulnerable populations, including low-income families with young or elderly members. While the study notes these disparities aren’t critical for public health now, they may indicate worse outcomes during future heatwaves.