Commissioner for Labour Sam Hui said he and his colleagues have questioned the sensitivity of Hong Kong's heat stress warning system after it remained at the lowest amber level on Sunday despite record-high temperatures, prompting a review of the existing mechanism.

Speaking on an RTHK radio programme on Tuesday, Hui acknowledged that he and his department had questioned the system's response while monitoring temperature fluctuations over the weekend.

"Frankly speaking, over the past two days, Hong Kong's temperatures have been among the highest on record," he said.

"On Saturday and Monday, when my colleagues and I were monitoring the temperature changes, we noticed that the heat stress warning level didn't escalate. That left us with a lot of question marks as well."

Hui said that the Labour Department is collaborating with the Observatory to explore enhancements to the mechanism.

He explained that the current system is based on the Observatory’s heat-stress indicators, which were originally designed to reflect Hong Kong’s distinctive humidity and hot climate.

These indicators are highly sensitive to humidity but assign relatively less weight to thermal radiation from direct sunlight compared with other international systems.

"What we are now considering is whether, on top of the original design, we need to adjust the activation threshold for a higher-level warning under unusually high temperatures – so that the system better reflects the overall severity of extreme heat conditions," he said.

He also noted that the department is examining whether to rebalance the weighting of the indicators, so the system more accurately captures severe conditions during extreme events, while still preserving the original framework designed for Hong Kong's unique climate.

The amber alert, which has been in effect since 7am on Tuesday, indicates that heat stress in certain work environments is high.

The extreme heat is expected to persist, with the Observatory forecasting maximum temperatures of 33 to 34 degrees Celsius in urban areas over the coming days – and a bit hotter in the New Territories – under the influence of a southwesterly airstream.


Edited by Aaron Tam