[anigbrowl]

Why bother with heaters? A plastic cap in front of the tubular 'hood' should work just as well and is a one-off cost. In the photo you can see the problem is the snow piling up inside the tubular shade. Cap the tube and gravity will do the rest.

[janzer]

Notice the sign to the right of the signal. Even though it is a straight vertical surface it's covered as well. Blowing wet snow will stick to just about anything.

[marze]

Snow can be sticky and sticky snow would stick to a plastic window.

[anigbrowl]

OK, heaters it is I guess. I grew up in a wet climate and when we got snow it was too heavy to stick to anything but the ground. D'oh, for assuming snow was snow.