Hong Kong lowers trigger threshold for Heat Stress at Work Warnings

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The enhanced system took effect on 28 August 2026, allowing higher-level alerts to be activated sooner during periods of extreme heat.

Hong Kong's Labour Department (LD) has further enhanced the Heat Stress at Work Warning (HSWW) system by lowering the threshold for triggering warnings during periods of extreme heat. The enhanced mechanism took effect on 28 August 2026.

Under the enhanced system, two new conditions have been introduced to strengthen heat-stress protection for employees working in hot weather or high-temperature environments:

• When the “Extremely Hot Weather” Special Alert issued by the Hong Kong Observatory is in effect, the monitoring threshold for triggering a higher level of HSWW will be lowered, enabling the early activation of a higher level of warning.
• When the measured temperatures generally over Hong Kong reach 35°C or above, apart from lowering the monitoring threshold for triggering a warning, the warning level will be raised by one level automatically, i.e. from Amber to Red, or from Red to Black.

The LD introduced the HSWW system in 2023 and enhanced it on 20 April 2026 by incorporating heat-stress data from nine additional monitoring locations alongside the Hong Kong Heat Index measured at King's Park as part of the issuing criteria.

However, despite record-breaking temperatures in early August, the HSWW remained at Amber Warning level, prompting public discussion over whether the system was sufficiently responsive during periods of exceptionally hot weather.

The LD said the latest enhancement is intended to better protect employees from heat-related risks amidst increasingly frequent extremely hot weather associated with climate change. The department added that it will continue to review the operation of the system and make improvements, such as studying whether to include other monitoring data such as the Wet Bulb Globe Temperature as one of the indicators of the system.

The LD stressed that the enhancement of the system will not impose additional work for employers and employees. Employers and workers should continue to pay heed to the level of the HSWW issued by the LD and make corresponding work arrangements.

Employers shall conduct heat-stress risk assessments for employees working in hot environments, and based on the assessment results and the risks of heat stroke faced by employees at different levels of the HSWW, implement the heat stroke prevention measures recommended in the Guidance Notes on Prevention of Heat Stroke at Work.

These measures may include:

• Rescheduling work periods
• Setting up shade covers
• Providing ventilation and heat dissipation equipment
• Reminding employees to replenish their water and rest in a timely manner

In addition, employers should keep assessment records, explain the assessment results to employees, and give appropriate instructions to minimise the heat stress at work.

The LD also encouraged employers to arrange on-site heat-stress risk assessments, taking into account the special circumstances of their work nature and workplace, such as geographical locations and specific working environments. Employers can also seek assistance from occupational health professionals to develop appropriate preventive measures.

The department reminded that employers who fail to provide suitable heat-stroke prevention measures and thereby endanger the health of employees may face prosecution. Inspections and enforcement actions targeting workplaces with a higher risk of heat stroke will continue to be stepped up to safeguard occupational safety and health.

Image / HKSAR Government Press Releases