The daily variation of ground-level ozone (O₃), a harmful pollutant, is positively correlated with air temperature (T) in many midlatitude land regions in the summer. The observed temporal regression slope between O₃ and T is referred to as the “ozone-climate change penalty” and has been proposed as a way to predict the impact of future climate warming on O₃ from observations. Here, we use two chemical transport models to show that the O₃-T correlation is primarily due to the meridional advection of both fields, as opposed to direct temperature-dependent chemistry or emissions. Furthermore, the magnitude of the O₃-T regression (dO₃/dT) can be estimated by the ratio of the time-mean O₃ and T meridional gradients. Consideration of expected changes in the meridional gradients of T and O₃ due to climate change indicates that dO₃/dT will likely change, and caution is needed when using the observed climate penalty to predict O₃ changes.