How this works
Questions
Is it safe to go out in the haze today?
It depends on the current NEA reading and on who you are. The home page answers this for your region and group, using NEA's latest 1-hour PM2.5. Healthy adults can go about normal activities when the 24-hour PSI is 100 or below, and are advised to reduce prolonged or strenuous outdoor exertion from 101.
What is the difference between PSI and PM2.5?
PM2.5 is the concentration of fine particles in the air, in µg/m³. The PSI is NEA's index built from several pollutants, and during haze PM2.5 almost always sets it. NEA recommends the 1-hour PM2.5 for deciding on immediate activities and the 24-hour PSI for planning ahead.
What PSI is unhealthy in Singapore?
NEA's bands for the 24-hour PSI are Good (0 to 50), Moderate (51 to 100), Unhealthy (101 to 200), Very unhealthy (201 to 300) and Hazardous (above 300).
Do I need an N95 mask?
Only if you must be outdoors for several hours. NEA suggests a well-fitted N95 for healthy adults when the PSI forecast is above 300, and for the elderly, pregnant women and people with heart or lung disease above 200. Surgical masks do not filter fine smoke. N95 masks are not made for children, so keep them indoors. If you have trouble breathing at rest or on exertion, check with a doctor first.
How accurate is the haze forecast?
The forecast is a calibrated Copernicus CAMS model, and it can be wrong when wind shifts suddenly or fires flare up. Every forecast is saved and compared with what NEA actually measured. The results are in the measured accuracy section of this page.
How many cigarettes is the haze equal to?
Breathing PM2.5 at 22 µg/m³ for 24 hours carries about the same risk of early death as smoking one cigarette (Berkeley Earth, 2015). It is a long-term average, a rough illustration and not a literal dose. Haze smoke and tobacco smoke are different.
The answer at the top
“Should I go out now?” uses NEA's latest 1-hour PM2.5 reading for your region, which NEA recommends for deciding on immediate activities. Each PM2.5 band is matched to the NEA advisory row it corresponds to (Normal → Moderate, Elevated → Unhealthy, High → Very unhealthy, Very high → Hazardous). The 5-day outlook uses the expected 24-hour PSI, which NEA recommends for planning ahead.
NEA health advisory (24-hr PSI)
| PSI | Healthy adult | Child, elderly or pregnant | Heart or lung condition |
|---|---|---|---|
| Good 0–50 | Normal activities | Normal activities | Normal activities |
| Moderate 51–100 | Normal activities | Normal activities | Normal activities |
| Unhealthy 101–200 | Reduce prolonged or strenuous outdoor physical exertion | Minimise prolonged or strenuous outdoor physical exertion | Avoid prolonged or strenuous outdoor physical exertion |
| Very unhealthy 201–300 | Avoid prolonged or strenuous outdoor physical exertion | Minimise outdoor activity | Avoid outdoor activity |
| Hazardous Above 300 | Minimise outdoor activity | Avoid outdoor activity | Avoid outdoor activity |
1-hr PM2.5 bands (µg/m³): Band I Normal 0–55, Band II Elevated 56–150, Band III High 151–250, Band IV Very high ≥251.
The forecast
Copernicus CAMS global PM2.5 forecast (0.4° grid, about 45 km, 3-hourly, interpolated to hourly), calibrated against NEA's live readings from the past 48 hours: a multiplicative bias correction, plus the current error fading out over about 12 hours. The likely range is the typical recent error, widening with lead time.
The 24-hr PSI outlook is computed from the forecast PM2.5 using NEA's published PM2.5 sub-index breakpoints (a rolling 24-hour mean). During haze, PM2.5 almost always sets the PSI. Forecasts are estimates and can be wrong, especially when wind shifts suddenly or fires flare up.
Cigarette comparison
Breathing PM2.5 at 22 µg/m³ for 24 hours carries about the same risk of early death as smoking one cigarette. It compares health risk, not the smoke you inhale.
So far today adds up each hour's reading since midnight.
It is a long-term average, a rough illustration and not a literal dose. Haze smoke and tobacco smoke are different.
Staying indoors with windows closed and a HEPA air purifier lowers what you actually breathe.
Sources: Berkeley Earth, 2015; Pope et al., 2011.
Measured accuracy
Every hour the forecast is saved as issued, then compared with what NEA actually measured. Numbers are the average miss in µg/m³ (lower is better), next to the raw Copernicus model and the simplest guess, “same as now”. An alert counts as caught when we forecast PM2.5 above 55 and it happened.
| Ahead | This site | Raw CAMS | Same as now | Unhealthy-air alerts caught |
|---|---|---|---|---|
| 6 h | ±23 | ±84 | ±27.6 | 100% |
| 24 h | – | – | – | – |
| 48 h | – | – | – | – |
| 72 h | – | – | – | – |
| 96 h | – | – | – | – |
3 forecasts since 2026-10-15. Raw data is public in the project repository.
Data sources
- NEA via data.gov.sgLive 1-hr PM2.5 and 24-hr PSI for 5 regions
- NEA news RSSHaze situation updates and announcements
- NEA historical PSIHourly 24-hr PSI since April 2014, used to compare this week's peak with past years
- Meteorological Service Singapore24-hour weather forecast
- Malaysia DOE APIMSLive Air Pollutant Index for Malaysian stations
- NASA FIRMS (VIIRS)Satellite-detected fires in Sumatra, Borneo and Malaysia
- OpenAQLow-cost community air sensors on the map, mainly AirGradient
- Copernicus CAMS via Open-Meteo5-day PM2.5 smoke model; Indonesian city estimates
- ECMWF via Open-MeteoWind at 850 hPa (about 1.5 km up) and rain forecast
- ASEAN Specialised Meteorological CentreRegional haze outlook and hotspot maps (reference)
- MyCMAQ (MetMalaysia)Malaysian air-quality forecast maps (reference)
Contains information from NEA made available under the Singapore Open Data Licence. Contains modified Copernicus Atmosphere Monitoring Service information. Weather data by Open-Meteo.com (CC BY 4.0). Fire data from NASA FIRMS. Community sensor data from OpenAQ.
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