Hong Kong vows to revamp heat stress warning system by month’s end

Authorities are aiming to revamp a heat stress warning system by the end of the month after it was deemed inadequate by former Observatory chiefs amid a historic heatwave.

Hong Kong saw a record-breaking heatwave in summer 2026. File photo: Kyle Lam/HKFP.

Labour and welfare chief Chris Sun said on Tuesday that the government would look into whether the warning system could be better tailored to Hong Kong’s weather, adding that the thresholds under its three-tier colour-coded warning system could be reviewed.

“Regarding the system thresholds, we need in-depth discussions with the relevant experts, especially those from the Observatory, to to clearly define how the system will be triggered,” he said in Cantonese.

“Our goal is to complete the work as soon as possible, make adjustments where possible, and put them into use,” Sun added. He said that the Labour Department and the Observatory would aim to revamp the system within the month.

Record heat

Commissioner for Labour Sam Hui said last week that his department will revamp the city’s heat warning mechanism after former Observatory chief Lam Chiu-ying called the mechanism “decorative” for issuing only the lowest alert during record-breaking temperatures.

Hong Kong Secretary for Labour and Welfare Chris Sun attends the first meeting of the eighth Legislative Council (LegCo) on January 14, 2026. Photo: Kyle Lam/HKFP.

Hui said that his department “had a lot of questions” when the Observatory recorded soaring temperatures earlier this month. On August 9, the Observatory reporting 36.9 degrees Celsius at its Tsim Sha Tsui headquarters under the influence of Tropical Cyclone Dolphin.

In addition to air temperature, the city’s customised Hong Kong Heat Index also takes into account other factors that determine how hot it actually feels, including humidity, wind speed, and solar radiation.

Hourly rest arrangements for outdoor work in times of Heat Stress at Work Warning. Photo: Labour Department website screenshot.

Weightings for those factors in the calculation of the index are determined based on hospital admission figures for the general public.

A reading of 30 on the index triggers the amber warning, and for the red or black warning to be issued, the index must reach 32 and 34, respectively. However, neither the red nor black warnings have been triggered since the system was introduced in 2023.

The index is not binding upon employers.

It follows that the Labour Department’s Heat Stress at Work Warning system has never triggered work stoppages, which are recommended for workers with heavy physical workloads when the red or black alerts are activated.

Labour chief Sun said on Tuesday that he was confident Hui would build on past experience operating the warning system in the department’s review, taking into account society’s concerns as well as the effects of climate change.