training in the heat is pure draining me

Honestly the last two weeks have been mental. Same sessions I've been doing for months and I'm coming out of them absolutely battered. It's the heat, right, it just takes more out of you than you realise. I've not changed anything — weights, sets, timing — but I'm hitting a wall about two thirds through every time. Started drinking way more during the session itself rather than just before and after and tbh that's helped a bit. Not fixed it, but helped. The one thing I'm not doing is cutting the session short. I'll drop a bit of intensity if I have to but I'm not leaving early. Mind you I did have to sit on the gym floor for a solid five minutes after squats on Tuesday so maybe I'm being a bit daft about it.