The facilities at Tulsa are very nice. The barns are less than 10 years old, and are pretty well ventilated. I haven't been there for a mid-summer show, so I really don't know for sure, but I'd think it'd be better than most places for staying reasonably cool, as the barns are high-roofed, and pretty well open to the north and south. Electricity is just marginal, so I would bring a generator if I had one (and plenty of cord, as I'm sure it'll have to stay outside). Wash racks are pretty nice, but water pressure is poor - plan on washing early or late or when alot of other folks are doing something else if you can. Tie outs are good, and not far from the barns, but there is no shade there, and don't expect to be able to tie to your trailer, either (I can't think of anyplace to park them that wouldn't be on pavement). I'm assuming you'll be showing in one of the bigger arenas - they're air conditioned, and have fairly nice seating. Restrooms are nice, and there're plenty of them - at least one set in the barns has showers and dressing rooms.
Can't think of anything else right now - if you have any more specific questions I'm sure I or someone else here can help.