About

Data sources

Contains information from NEA and LTA 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. AQI station data from the World Air Quality Index Project (waqi.info).

How the advice works

The answer at the top of Now uses two NEA readings for your region:

• The 1-hour PM2.5, for the next few hours, read with NEA's personal guide (stricter for the elderly, pregnant women, children and people with heart or lung disease).
• The 24-hour PSI, for planning the day, read with NEA's health advisory below.
• "Should I go out now?" follows the 1-hour PM2.5, as NEA advises for the next few hours; the 24-hour PSI is used only when there is no PM2.5 reading. The 5-day outlook uses the expected 24-hour PSI; the hourly plan uses the PM2.5 guide.

NEA health advisory (24-hour PSI)

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. Personal guide for the next hour: band II reduce strenuous outdoor activity (vulnerable persons avoid it), band III avoid strenuous outdoor activity (vulnerable persons avoid all outdoor activity), band IV minimise all outdoor activity (vulnerable persons avoid it). Source: NEA PSI and PM2.5 guide.

How the forecast works

The forecast starts from Copernicus CAMS, the EU's global atmosphere model. It usually gets the timing of haze right but is often far off on how bad it gets, so Haze Lah corrects it against what NEA measured over the past 48 hours.

Technical detail: 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.

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.

53 forecasts since 2026-10-15. Raw data is public in the project repository.

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.

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What's new

Version 1.6.2, 24 Oct 2026

• Plan your day, in one cardPick running, cycling, football or a walk and how long you'll be out. Your best time, the hours from now and the fine dust you'd breathe, all in one card, with bars sized to show the changes.
• New forecastOne answer up top, then a 48-hour graph you can drag: PM2.5 with its likely range, the wind and the rain. See how accurate the forecast has been.
• Fly in from spaceThe globe now opens on the whole Earth and flies down to Singapore, and it loads faster. Tap anywhere to skip.