HKEX did not open Monday morning:

Some better news for HK, the storm warning has been lowered a notch to red. HKEX will thus open for trade at the beginning of the scheduled afternoon session

  • from 1.30pm local time

As I post its going on to 11.30am in HK.

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As an FYI:

There are three levels of warning: AMBER, RED and BLACK.
The AMBER signal gives alert about potential heavy rain that may develop into RED or BLACK signal situations. ...

The RED and BLACK signals warn the public of heavy rain which is likely to bring about serious road flooding and traffic congestion.