I have found the MOST comfy warm weather jammies EVER, and they are totally cheap.
They are a one piece jammie tank on top shorts on bottom, and just a little elastic at the waste to give it a little bit of billowing in the middle.
I got it at Love Culture in the Galleria on sale for NINE dollars on Saturday and basically lived in it all weekend. Buy as many as you can while they are still available. You will sleep like a baby but look like a Diva.