This GIF animation of thermal images from Japanese blog IT Media shows how how Apple's coolest computer gets under maximum stress.
The computer doesn't really get too hot at all, and the combination of its ventilation design and lack of a hard drive seems to work quite well.
In sleep mode, the computer doesn't produce any distinguishable heat, and sleeps at just 86.54 degrees Fahrenheit (30.3 deg Celcius). Watching a clip on QuickTime for 15 minutes only took the Apple computer to 95.18 degrees Fahrenheit (35.1 deg Celcius).
The machine only got really hot when pushed to its limit using Cinebench and other hardcore apps. It then reached its max temperature of 118.76 degrees Fahrenheit (48.2 deg Celcius).