Linearly Scale Light Temperature I want to have a plane which goes from temperature x to temperature y with respect to one of its sides. I was looking into drivers but this doesn't seem to accommodate geometry, only scale and position. Is there anyway that I can linearly increase the emission temperature of a plane surface with respect to the length of one of its sides; say its width.
You can map color temperature like you can map any other shader value with nodes, no need to involve drivers unless required.



Just use either direct texture coordinates as input for a Color Mix node, or use World Coordinates from a Geometry node instead.

Separate the desired direction, use math nodes to adjust length of progression, then feed it into a Color Mix with each temperature plugged to a Color socket.



Alternatively for more complex progression patterns you may use a gradient texture.