What is the cause of orange sky glow? I live in the Netherlands and recently I have been seeing an orange glow in the sky at night, in the northwestern direction. What is the cause of this? And why is it in the northwestern direction (I have seen it a couple of times recently, all in the same general direction).
 A: What kind of Orange and how much of the sky did it fill?

Low pressure sodium lights are common in lighting cities and highways. Is there a big city/freeway northwest of you? I suppose under the right conditions you could see sky glow from a large city a long way away.

If you are at a very dark clear site (unlikley in the Netherlands) it could be zodiacal light - sunlight reflecting off the dust that fills the solar system. Although I don't know you could see it with the naked eye at a regular site
A: 
Here from Delft, it looks like this in the north east direction.
Rotterdam is my this direction of my view. 
But I doubt it's that. Because the sky is too bright. And it's daily.
Also, the Hague is in the other direction and closer, and it's never orange that side. 
A: this answer is probably a bit on the late side but it seems that most recent comments still haven't given the answer to this question yet. 
The most likely cause of the orange hue in the night skies are the plenty of industrial sized green houses in our country. This is noticable between the hague/delft and rotterdam where there is more greenhouse than actual grass/green (explaining why Martin can see it in the direction of rotterdam, but no such hue in the direction or the hague.)
Though from experience i can tell that a single decent sized greenhouse is plenty to fill the air. I come from a small village where in the northern part there are some big green houses. The hue is especially common in winter and if you take a nightly hike near near one of the green houses it is almost like night turns into day so bright near them. 
tldr, its green houses cause the Dutch want to be efficient with their time growing flowers vegetables and fruits to sell. 
