HK's sky condition has been pretty bad for years but the last couple years had became even worse then ever so you can understand the difficult situation we're facing now.
When the wind blowing from the North the floating particle in the sky will severely increase and according to the media's saying it's because a lot of low qualitied power plants have been built and running around the Canton area which provided so many toxic partcles in the air and hance HK had to take them unwillingly.
Now we might have fewer and fewer days of clear skies and some star gazers had to flee to Mainland or other districts for the better sky.