I skied on Mt. Hood last July - pictures here:
https://flickr.com/photos/rachelv/sets/72157601107104956/
The snow was actually really nice in the morning. They open the lifts at 7 or 7:30, and until 11 or so it was really nice. I'd compare it to early spring conditions in general -- a little soft, but still surprisingly firm. After 11 or so it started to soften up really fast, and by 1 when the lifts closed things had gotten pretty goopy. The parts they'd salted were noticably firmer, the parts they hadn't were pretty exhausting to ski.
Overall it was great, though. I was surprised by how nice things were in the morning, and in the afternoon I was still too excited to be skiing in July to mind how soft it was.
I was wearing flannel pants under insulated ski pants, and a long-sleeve t-shirt and lightweight fleece on top. That was enough. When the wind kicked up I was a little chilly, but overall I was on the warm side. I'd say just wear 2 or 3 thin layers, light gloves, and adjust as you need to.
You're going to have a fantastic time.