I go to the 5.45am class, but I would struggle to WOD in the avo - however since we're in winter now (I'm in New Zealand) I'd love some sunshine.

Following, I have issues with the heat too.

Here's my tips/suggestions:
1) Make sure you intake plenty of hydration during the day and then pre and post WOD. This should be water or other type of electrolyte fluids.
**BTW - Coffee (hot or iced) does not count as hydration.
2) Wear lighter-weight clothing and/or water-wicking clothes.
3) Accept the fact that you may need to just go a little slower.

And don't worry .... "Winter is Coming"

Our gym refuses to run the AC. A lot of of our gym is cops, firefighters, ex-military, so I think they have a higher misery standard than average. On one hand, it's stupid hot at noon. On the other hand, at the 5am class the gym has been closed up all night and so it's kind of an oven. I think the 8:30 class works out best at our gym as far as balancing stored heat vs sun heat.

Lots and lots of water helps. Drink it all day, every day. If you're going to be doing anything outside or in the sun (like if your gym has bay doors that will be open) put on sunscreen, I was surprised how much it kept me from overheating.

Think of heat acclimation like DOMS. You know how when you don't work out for a month, you get ridiculous DOMS when you go back, and that can be motivation to not start skipping out? Heat acclimation is the same way. Keep going and you'll get used to it, stop going and you'll have a harder time with the heat when you get back.

our box is air conditioned, as it's part of a regular gym.

That said I think you're doing it right. Keep yourself hydrated and slow down when you need to and your body will continue to adjust itself to what you are demanding of it.

FWIW, I'm almost always an evening workout guy, but when I spend my vacation week at the Outer Banks in NC I almost always hit the local CF box as early as they open to avoid the heat. Last year I got lucky and had a day with highs in the 70s. That box also does not announce the WODS, so you have no idea what you're going to get.

I asked one of the owners if they were going to run the AC when we move to the bigger facility next month. He got quite the belly laugh out of that.

I do six am, and this morning we were all sweating like pigs! I'm trying to drink extra water. Yesterday I was planning to do an evening class but it was 104F for the 6 pm class. Running in the parking lot at that temp sounds awful... I do know I get used to it but this is our first 100 degree week and I am not yet!

My old CF gym did not have AC but it never got to be too bad. My new CF gym does have AC so that won't be an issue, though it still gets pretty hot in there sometimes!

Boston will have a few hot, humid, sticky days but the Atlantic Ocean is a giant heat sink and usually cools things off on the coast a bit.

I live in FL, we go to the 6am and I go back in the afternoon to work on my goats...it's running at 100 today, no air. Water and I guess you acclimate. We moved down here from NH, so it doesn't come naturally...you just get your body used to it. I run outside in the afternoon as well, just takes some time to get the breathing...definitely listen to your body