We were just there Sept 3-6 and only used our AC only once. Nights were low 60s. Hiking in the day can get quite hot (80-90s). Use your shade and carry LOTS of water.

Well of course it's hot but as another reviewer mentioned, its 7-10 degrees cooler than Moab if that helps, but it's very dry and lovely at night.

It was pretty hot during the day, but evenings and mornings were okay. You just have to do activities early or late. I would not recommend doing anything strenuous during the day. We visited shops and restaurants during the day.

Not unbearably, and the nights are cool.

August? It was 110 degrees in June. August is hotter.