<p>As global warming accelerates, surface ozone (O₃) pollution under high-temperature conditions poses growing environmental and health risks. This study analyzes observational data from China and the United States to assess how rising temperatures impact ozone formation. Results show a stronger ozone–temperature sensitivity in China, with climate penalty factors of 2.9 μg·m⁻³ °C⁻¹ vs 2.1 μg·m⁻³ °C⁻¹ in the U.S. Structural equation modeling reveals that direct temperature effects dominate, while photochemical modeling attributes China’s heightened response to elevated NO<i>ₓ</i> and VOC emissions. Under prolonged heat events, ozone increases plateau or decline in the U.S., but remain pronounced in China. During COVID-19 lockdowns, emission reductions curbed ozone levels in China but not in the U.S., where meteorological factors prevailed. These findings highlight the urgent need for region-specific emission control, improved heat-adaptive air quality management, and alignment with climate goals to mitigate ozone pollution in a warming world.</p>