I build my brooder and hung a thermometer in there. it's in the shed, in the shade, door and windows open and it's 83 degrees without a heat source.
Am I asking for trouble?
the contraption is cardboard. not roof (yet - but that would be chicken wire)
Potentially.
They need a spot that's warm enough and a spot that's cool enough.
Of course we can't get cooler than the ambient air when our steamy summers heat up.
Make sure that they can get away from the brooder heat source to cool off as much as possible.
Also, take your temperature readings at chick height -- it might be much cooler on the ground. I put my thermometer on a brick since that's about as tall as a day-old chick.