Everything I've read says cockatiels are comfy in temps between 65 and 80. My old place was hot in the summer, hard to cool down, but here is better. I'm gradually lowering the temp from that 78 to 80 they used to stay at, to the 73 I think we will all be comfy at. If I had my preference, I'd be at 65, LOL! But, for my electric bill's sake, I'll keep it a bit higher.

As for the cover, you'd have to try it out and see. Some birds don't mind them, others don't like the change. You can try a sheet, to see how he likes his cage covered. If he is okay with it, then you can get a cage cover if you want. I always used sheets..