Labour minister Chris Sun on Thursday said the government is working to update guidelines to prevent heat stroke for workers so that it won't be just about how hot the day is.

He said officials are studying whether to add the observatory's heat index as one of the reference factors, calling it a scientific and objective indicator of the actual weather situation.

"As we all know, for heat stroke, besides the temperature, it's also about humidity, whether [the worker] is under direct sunlight, work intensity, and whether [the worker's] clothing is permeable," Sun told reporters after attending an event.

He said officials will update the guidelines as soon as possible so that employers and workers can better iron out arrangements such as water breaks and work intervals.

Asked whether employers must follow the guidelines, the minister said bosses are legally responsible for ensuring workers don’t suffer from heat stroke.