Singapore, 24 July 2023 – The Ministry of Sustainability and the Environment (MSE) and the National Environment Agency (NEA) have launched a Heat Stress Advisory for the public. The advisory will help the general population make more informed decisions on undertaking prolonged outdoor activities, so that they can minimise the risk of heat stress and heat-related illnesses. The Heat Stress Advisory can be accessed via the myENV app and weather information website (www.weather.gov.sg).
2 With climate change, many countries in the world, including Singapore, are seeing rising temperatures. The last 10 years from 2013 to 2022 was Singapore’s warmest decade on record. On 13 May 2023, a 37 degrees Celsius air temperature was recorded at Ang Mo Kio, equaling the previous record set on 17 April 1983.
3 It is therefore important for members of the public to adapt to rising temperatures. MSE and NEA have developed the Heat Stress Advisory in consultation with the Ministry of Health’s Heat Stress Guidelines Expert Panel . The Advisory aims to provide information on areas of Singapore where people may experience heightened levels of heat stress and how the general population should adapt for prolonged outdoor activities.
4 The Advisory, detailed in Annex B, follows three levels of risk of heat stress – low, moderate, and high – and is based on the Wet Bulb Globe Temperature (WBGT). The Advisory will provide simple tips for members of the public to adjust their activities, take protective action, and wear appropriate attire depending on the prevailing heat stress levels.
5 The WBGT is an internationally recognised measurement that reflects the main environmental factors contributing to heat stress. Besides air temperature, WBGT is also affected by humidity, wind speed, and solar radiation. Details of the WBGT are outlined in Annex C. The WBGT readings are derived from an islandwide network of nine sensors operated by NEA. There are plans to expand the network over the next two years.
6 Prior to undertaking prolonged outdoor activities, members of the public can check the Heat Stress levels on the myENV app or on the weather information website (Annex D). The myENV app displays the Heat Stress levels based on the WBGT measurements from the sensor closest to the user’s location. Existing users of myENV will need to update the app to the latest version to access the heat stress feature.
7 While the Advisory provides general guidance, members of the public should also take into consideration individual circumstances, such as health, age, duration, and intensity of intended outdoor activities.
8 Specific segments of the public with specific conditions or those who are required to be engaged in prolonged outdoor activities should refer to the respective sectoral guidelines. For example, companies and workers should refer to guidelines from the Ministry of Manpower, students should follow their school’s guidelines, and Singapore Armed Forces and Home Team personnel and National Servicemen should refer to their own sector-specific guidelines.
 The composition of the Heat Stress Guidelines Expert Panel is in Annex A.
Annex A: Composition of the Heat Stress Guidelines Expert Panel
||Designation and Affiliation at time of appointment to Heat Stress Guidelines Expert Panel
|Prof Chia Kee Seng (Chairperson)
||Professor and Founding Dean of Saw Swee Hock School of Public Health, National University of Singapore
|A/Prof Jason Lee
||Associate Professor, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore
|A/Prof Lee Hock Siang
||Senior Consultant, Occupational Safety and Health Division, Ministry of Manpower
|A/Prof Roger Tian
||Senior Consultant, Singapore Sports & Exercise Medicine Department, Changi General Hospital
|A/Prof Mark Leong
||Senior Consultant, Department of Emergency Medicine, Singapore General Hospital
|LTC (Dr) Alexander Gorny
||Public Health Physician from HQ Medical Corps, Singapore Armed Forces
|Mr Cheong Wee Kiong
||Deputy Director (Forecast Operations Department), Weather Services Division, Meteorological Service Singapore, National Environment Agency
|Mr Jue Tao Lim 
||Scientist, Environment Epidemiology & Toxicology Division, National Environment Agency – Environmental Health Institute
 1 LTC (Dr) Alexander Gorny and Mr Jue Tao Lim have since left their original institutions. LTC (Dr) Alexander Gorny is now a research assistant based in Denmark at the Aarhus University Hospital, and Mr Jue Tao Lim is an Assistant Professor at the Lee Kong Chian School of Medicine, Nanyang Technological University.
Annex B: Heat Stress Advisory
Annex C: Computation of the Wet Bulb Globe Temperature (WBGT)
The WBGT is a widely used heat stress indicator that takes into account air temperature, relative humidity, wind and solar radiation that could contribute to heat stress. WBGT is calculated based on the weighted averages of natural wet-bulb (Tnwb), dry bulb (Td), and the black globe (Tg) temperatures.
The equation used to calculate the WBGT is:
WBGT = 0.7 Tnwb + 0.2 Tg + 0.1 Td
Td is the temperature of the ambient air measured in the shade. (This is the air temperature values people are familiar with, and are indicated in MSS forecasts and weather reports)
Tnwb is the Natural Wet Bulb temperature, which is measured by a thermometer covered by a wet cotton wick that is exposed to the natural prevailing air movement as well as radiation. It represents the integrated effect of air temperature, humidity, and wind speed. Tnwb is always lower than the dry bulb temperature. The closer together the values are, the more humid it is. At 100% relative humidity, the Tnwb is equal to the dry bulb temperature.
Tg is the temperature measured by a dry bulb thermometer that is inserted into a standard black metal globe and it represents the integrated effect of air temperature, wind speed and radiant heat.
An example below illustrates how WBGT values varies with humidity and globe temperature (solar radiation, cloud cover), while having the same air temperature.
||Natural Wet Bulb Temperature (Humidity%)
||Black Globe temperature
(i) Heat Stress Advisory on the myENV mobile app
(ii) Heat Stress Advisory on MSS website