Still, I empathize with your desire to have shoes that breathe well on warm days. Scarpa's Vento Mid ($130) is a good, light boot, with over-the-ankle coverage and fabric-and-leather construction that offers reasonable support and good breathability. A similar boot with slightly taller construction is the Chameleon Ventilator from Merrell ($110). It's designed with hot weather in mind, and has special breathable mesh panels on each side, along with suede leather for durability. Lastly, Boreal's Midi ($140) is a beautifully made light leather hiking boot that has a wicking liner to help keep your feet cool and dry.
Any of these would work well, I think.