Fire in the Sky

Photo by Cliff Mass, 2010

I have never dealt firsthand with fire. I've never had a job having to do with fire, nor have I ever actually seen a wildfire, except for on TV. I have however, seen the red sky that is the product of the smoke from a wildfire. Yes, it is pretty and cool looking, but it is also slightly terrifying. This means there is a fire so big, that it is blocking out the sun.
In August 2015, there was a wildfire in central Washington that had smoke blow over into Oregon, around the Mt. Hood area. The picture below was taken on Highway 97, west of Wasco, Oregon.

Photo by Thomas Boyd, 2015

So what is it that makes the sky so red when there's a fire? Well, it's smoke. More specifically, the light is being scattered by the smoke particles. This is called Rayleigh scattering, and is also the reason the sky is blue. When there isn't a fire, the small particles in the air can scatter incoming light into various directions, and scatter short wavelengths (purple and blue), much more than they scatter long wavelengths (red and orange). Normally, the blue light then bounces around the particles and then down to Earth, making the sky appear blue to us. 

Add in smoke from a fire, and you've added in even more particles to be scattered around. This makes it easier for the light to scatter the long wavelengths, since it has more to bounce off of. So naturally, oranges and reds get scattered and bounce down to earth, making the sky red. 

In cases like the one in Washington, however, there was too much smoke, and didn't leave any room for those particles to bounce around at all. This caused the sky to turn black because of the ashes of the burning  materials.