His announcement on Thursday comes after concerns were raised this month, when only the lowest amber alert was issued despite record-breaking temperatures.
Hui said two new triggers have been, following discussions with experts at the Observatory, added to improve the system’s responsiveness to exceptionally high temperatures.
From Friday, he said, when the Observatory issues an extreme heat alert, the amber warning will be issued immediately, and the threshold for raising the warning level will be lowered to allow for an earlier activation.
He explained that if temperatures across Hong Kong reach 35 degrees or above, the warning will be automatically raised by one level – meaning if it reaches amber, a red warning will be issued, and the same applies from red to black.
Hui said he hopes the warnings will help employers and staff put mitigation measures in place faster.
“We expect this new arrangement will continue to give timely warning alert to workers working under heat stress caused by high humidity and poor air circulation as well as triggering earlier and higher warnings [about scenarios] of abnormally high temperatures especially for workers working outdoors,” he said.
He added the department would continue to collect data to assess the effectiveness of the improved system.