Why do I need to wear a jacket in the summer? It’s hot!
Even a mild case of “road rash” (caused by sliding across the pavement after an accident) will be uncomfortable for months - compare that to the few minutes of discomfort caused by wearing the jacket when it’s hot! In addition, having a 30+ mph wind blasting across your bare skin will give you a wonderful case of wind burn, and dehydrate you as well. Wearing a jacket when riding will actually make you more comfortable, regardless of the season.
