People and other mammals, however, generate their own heat and have body temperatures that are normally higher than air temperature. Gas molecules move haphazardly and move at random speeds. They continually run into one another, sometimes giving kinetic energy to neighbors, sometimes receiving kinetic energy. In this continual interaction, it would be statistically impossible for any large number of molecules to have the same speed.
Temperature has to do with average speeds.
You cannot establish by your own touch whether or not you are running a fever because there would be no temperature difference between your hand and forehead. If your forehead is a couple of degrees higher in temperature than normal, your hand is also a couple of degrees higher. The hot coffee has a higher temperature, but not a greater internal energy. Although the iceberg has less internal energy per mass, its enormously greater mass gives it a greater total energy than that in the small cup of coffee. No, a mercury thermometer would not be feasible if glass and mercury expanded at the same rate with increasing temperature.