Brettanomyces bruxellensis is a spoilage yeast particularly dreaded in red wines, where it produces volatile phenols with sensory properties that lead to wine spoilage. The development of this yeast often occurs during wine aging, especially during the summer. We show that in the Bordeaux region, the temperatures of some cellars rise significantly in July, August, and September. This greatly increases the growth rate of B. bruxellensis strains in both permissive and more unfavorable wines. Therefore, although temperature does not affect the specific formation rate of ethyl phenol, raising the wine temperature from 2 to 6 degrees C makes volatile phenols appear both earlier and faster, regardless of the wine or the yeast strain present. Closer control of active yeast populations and closer monitoring of aging wines is thus essential in the summer, particularly in cellars with poor temperature regulation.