The occasional max peak is predicted to increase significantly more than the baseline average. Increased variability in almost all climate features - in time, in space, in measured attribute - is the routine IPCC prediction. If the water vapor content of the air also peaks accordingly, taking the wet bulb temp with it, 50 - 55C temp peaks will occasionally turn lethal - killing most mammals caught in the open within a few hours. They will also kill many plants, including some trees. That's without catastrophe, such as runaway methane feedback.