Hot weather socks, my suggestion, go with Darn Tough Vermont 1/4 mesh, or Defeet Aireators, both are durable and breath very well. I prefer the Darn Tough line due to the use of Merino, the Defeets are synthetic.
Sockless hiking is far from crazy, it depends on the conditioning of your feet, the terrain and temperature, as well as the shoe, most importantly it depends on the person. Honestly, I have yet to get a blister in the last 3 yrs., not a single blister. I trail run sockless a few times a week for about 8 months out of the year because I hate how warm my feet get while running out on the hot rocky trail, as well as the loss of underfoot sensation and trail feel. Last weekend I did a relatively strenuous 3 day trip in the Gila Wilderness and hiked portions of the 2nd day sockless and hiked the entire 16 mile 3rd day sockless through canyon and countless stream crossings. Temps were warm (70-80F), dry and sunny. If I do wear socks I typically wear a pair of Darn Tough Vermont 1/4 mesh socks, they're light and breathable, as well as thin. But again, it definitely depends on the person, I'm also that dude who hikes shirtless once the temps rise above 75F, so to each his own.