Light waves are radio waves but radio waves may not be light waves. 

So what why does it matter?  Radio waves near the light spectum  (405 THz to 790 THz.) behave more like light and 2.4 Ghz is a very long way from a light wave.  Sitll it is more reflective as light is, and moisture will diffuse the ray, just as light becomes hazy on a humid day so do 2.4 Ghz waves.