The hot and humid summer in Hong Kong poses an increased risk of heat stroke to employees working outdoors (e.g. construction, cleaning, security, landscaping, etc.) or in indoor environments that lack air conditioning systems (e.g. electrical and mechanical staff). In addition, employees who are required to work near heat sources or heat-generating facilities (e.g. boilers) are also at risk of heat stroke. This Guidance Notes outlines various factors that employers have to consider when conducting risk assessments for employees, including working environment, work nature and personal factors, and introduces preventive and control measures that are applicable to different risk factors. It helps employers implement appropriate preventive and control measures according to the actual work situation, such as arranging suitable work and rest schedules, to reduce the risk of heat stroke posed to employees working in hot environments.