Mike Nelson wrote an answer about Fi'zi:k R1 Uomo Shoe - Men's on April 15, 2014
The Fizik R1 and R3 shoes both have uppers made of kangaroo leather and breathable mesh. The R1 actually uses more leather over the arch an instep of the shoe than the R3, This makes for better support and fit, but it will probably not translate to cooler feet on a hot day. Here is a top view of the shoe from http://www.fizik.com/shoes/road-shoes/r1-uomo/
If your feet are suffocating on super-hot days, look for a road shoe with a vents on the sole and a lighter synthetic upper with more mesh.