They're called thunderstorms. Very normal.
Another freak one happening right now. Ample warning by the HKO though. Winds of up to 110km/h. Hope no one gets stuck outside when the rain starts coming down.
The lightning has just killed off the Ma On Shan Line (now fixed) and the East Rail (not fixed).
https://twitter.com/mtrupdate/status...30555470032897
EDIT: now fixed.