As an aside, even many hunts are now relaxing the rules about attire during summer cubbing–because tweeds are HOT and dangerous. My hunt asks us to start the season (day 1) in rat catcher attire, but then the masters will make the call to allow club-branded polo shirts for the rest of cubbing. We have to wait for them to do that (don’t assume polos are ok until you are told they are), but they are usually quick to make the call. We go back to rat catcher attire in September until the formal season starts–unless it’s too hot!
I showed hunters for years and hated wearing coats on hot days. I am one of those people who do not do well in heat–would rather be freezing than hot! My first season hunting, we had a 90+ degree day in the formal season, but the masters did not relax the coats rule in time for people to opt out…hunted for three hours in a wool vest, stock tie, and Melton–it was awful, but I swear I had worse days at cooler temps in my polyester hunt coat in the show ring. At least wool breathes.
I will note, though, that in my years as a show photographer, when coats are excused, people tend to buy less photos (hunters). Even the best money shot over fences looks somewhat lesser when the rider doesn’t have a coat on.