The general rule of thumb is that in moderate dry heat thin loose-fitting absorbent clothing holds sweat and allows evaporation to more efficiently cool you.

In high humidity you go with bare skin so the sweat falls off because it isn't going to evaporate.

If your in the sun a wide brimmed hat creates shade and light colored clothing absorbs less heat.

It all changes when heat goes well over 100F. At those temperatures the air is dry but extremely hot. So high that exposure to untreated air is harmful. In those conditions you see heavier insulating clothing that shroud the body and create a micro-climate like a space suit. Think of traditional Arab dress where the entire body is covered.

Of course in high heat you need to slow down. And many cultures stop work in the heat of the day. A work day that runs 0800 to 2000 with a four hour break from 1200 to 1600 can be quite effective in the summer when its daylight until 2100. I have also seen jobs run from 0500 to 1300. The long lunch system has the advantage that the crews essentially start fresh two time a day when energy and concentration are at their best.