I'm using these for my smart mirror project, and tied them by index to the Yahoo Weather API.[1][2] There isn't a perfect one-to-one relationship between the API codes and the icons, but it's pretty close.

My one complaint about the icons is that they flow outside of the boundaries of what you'd expect them to be contained in, which can lead to some accidental overlap if you aren't careful with your margins.

[1] https://github.com/alaycock/SmartMirror/blob/master/public/j...

[2] https://developer.yahoo.com/weather/documentation.html#codes