Singapore's Heat Stress Advisory, jointly issued by NEA and the Ministry of Sustainability and the Environment (MSE), uses Wet Bulb Globe Temperature (WBGT) rather than plain air temperature to gauge heat-related illness risk. WBGT is a composite measure — it factors in humidity, wind speed, and solar radiation as well as temperature, which matters a lot in a humid tropical climate where the same air temperature can feel very different depending on conditions.
| WBGT | Level | Guidance |
|---|---|---|
| Below 31°C | Low | Generally safe for prolonged outdoor activity, with normal precautions. |
| 31–33°C | Moderate | Take more frequent breaks and stay hydrated during prolonged outdoor activity. |
| 33°C and above | High | Reduce intensity and duration of prolonged outdoor activity; vulnerable groups should take extra precaution. |
The advisory notes that individual circumstances — health, age, and the duration/intensity of the activity — matter alongside the WBGT reading itself. Groups needing extra precaution generally include the elderly, young children, and anyone with existing health conditions.
NEA operates an islandwide network of WBGT sensors — around 9 as of the advisory's launch, mostly at outdoor sports facilities, with plans to expand. Readings update every 15 minutes and reflect the average over the preceding 15-minute window, from the sensor nearest a given location.