Investors will still be able to trade in the city's financial market under typhoon signal number eight or above and during black rainstorm warnings from September 23.

Chief Executive John Lee made the announcement ahead of his weekly Executive Council meeting, saying Hong Kong has no valid reason to stop the financial market operating during severe weather conditions, when other major financial hubs are able to continue trading in such circumstances.

"Other securities markets around the world such as Shenzhen and Shanghai, they maintain trading even under severe weather conditions. Hong Kong is the only exception. Hong Kong is an international financial centre and there is no reason for us not to align with international standards," Lee said.

The CE said the move would consolidate the competitiveness of HKEx and raise Hong Kong's role as a trading corridor with the mainland.

Citing a public consultation exercise carried out by HKEx, Lee said about 90 percent of brokerages and banks support keeping the financial market open under severe weather conditions.

He said the implementation date in late September will give the trade enough time to prepare, and the relevant authorities will offer support to small brokerages to cope with the change.