I spent a lot of time riding in REALLY hot weather a couple of weeks ago. This week I learned that additional preparation is required for running at temperatures above 110°F for several hours.
You do NOT want to maximize the wind against your skin when the temperature gets extreme. Mesh suits, or wearing just a lightweight shirt, are NOT the right approach. You will actually stay cooler with a conventional suit with the vents adjusted so there is a more moderate air flow across your skin.
You should never ride without ATGATT anyway but in extreme heat, it’s even worse to be out riding in a t-shirt and shorts.
For my Riding Friends: “Riding Motorcycles in Extreme Heat”