I generally get through 2 t-shirts a day in the summer. However that's partly due to the fact that I'm becoming more and more miserly with age and will only put the AC on during the day when it's like 90+ and humid. Sometimes I'll sit at my DAW for hours and not even realize that I'm sweating bullets.
Recently I switched up my routine so that I shower before bed, not after. I sleep with the AC on so I don't sweat in bed, and it's great to be able to get up and go straight to the coffee without all of that toweling off nonsense. However that means that I have to switch t-shirts again since I figure the least I can do is not wear the one I just slept in

So sometimes I will even get through three t-shirts if it's hot. Laundry day is a pain, but at least I'm super fast with the t-shirt folding due to the Asian folding technique I got off YouTube years ago. Here's a better video than the one I learned it from.