METARs don't mean !!!!
The pollution pumping out of China is f*cking vast. With the dry monsoon the overall air flow is from the north - hence the pollution gets worse. The airflow takes the crap a long, long way south of HKG, so it takes a long, long time with a wind from the south for the air to be clear again.
A METAR showing it is a southerly and therefore claiming that the poor vis is not from pollution is crap.
HKG is a polluted !!!!hole - thanks to the money grabbing scum to the north. Japan, Europe and USA all had bad pollution - but the people demanded change and got it. The technology does exist. The Chinese leadership don't give a !!!! about the people, it is all about the profit, so no use of the technology which will reduce pollution and margins. In commie countries like China, people who speak out disappear so the drive for a better place to live which occurred elsewhere will not happen until the commies are gone.
The pollution in the air and food in HKG will shorten your life. Your kids will be sicker more often.
There are pilots who have had to quit CX on medical advice to themselves or family members.
Pollution is a big reason there is so much demand for base slots.