Oh girl I totally feel ya on this one! I am a Southern transplant and let me tell you I remember feeling like I was swimming in sweat my first time showing! Plus riding after work during the hottest part of the day feels like I’m riding on the surface of the sun.
Kerrits breeches will change your life. The ice fill tights and their regular breeches are like riding naked. I have both and LOVE them! They’re not as “fashionable” as TS or cavaleria toscana but so worth it. For tops, I found TS sun shirts to be the coolest and last the longest. They are a thinner fabric than kastel. Kerrits also makes sun shirts but they’re a little out there pattern wise for me!
Other things I recommend- when you get off don’t sit down!! I liked to sit and chat or watch others while my horse cooled off. Stay standing and untuck your shirt to catch a breeze while you groom/ bathe/ clean tack/ etc. Take off your helmet and boots or chaps right away.
Blast the AC in your car not directly at you. Try to point it in all directions so the whole car cools off. I can’t stand the cold air directly on my arms and face for very long so I end up turning it down even though I’m still sweaty below the waist.
Once you get home shower ASAP and then be naked at least on your bottom half for a while. It helps prevent the bumps.
I haven’t discovered a good bra solution but I’m pretty flat so maybe others can help.
I really appreciated your title! Stay cool! 