Clear Skies

One things which has been bugging me for the last week or so is: why do we have such clear skies for the 10th anniversary of the handover? Normally the sky would be an unpleasant brown colour at this time of year, but things have been amazingly clear for the past few weeks. Being able to see Lion Rock from Causeway Bay is not normal.

Have the barely regulated, highly polluting factories in the Pearl River Delta been ordered to shut down for a bit so that the world's press don't come away from the Handover anniversary with tales of chronic pollution?

UPDATE: possibly just a change in the local prevailing wind direction.