About Haze Now

It depends on the reading where you are. In Singapore, NEA's guide for the 1-hour PM2.5 says: Normal (up to 55), normal activities. Elevated (56 to 150), reduce strenuous outdoor activity, and vulnerable persons avoid strenuous outdoor activity. High (151 to 250), avoid strenuous outdoor activity, and vulnerable persons avoid all outdoor activity. Very High (above 250), minimise all outdoor activity, and vulnerable persons avoid all outdoor activity.

Everywhere else the US EPA's advice applies. Unhealthy for Sensitive Groups (101 to 150): sensitive groups reduce prolonged or heavy exertion. Unhealthy (151 to 200): everyone reduce prolonged or heavy exertion. Very Unhealthy (201 to 300): everyone avoid prolonged or heavy exertion. Hazardous (above 300): everyone avoid all physical activity outdoors. The page for your area shows the advice for the reading right now.

Both, for different things. NEA advises using the 1-hour PM2.5 for immediate activities and the 24-hour PSI forecast to plan ahead. The 1-hour PM2.5 covers only the last hour, so it changes quickly; the 24-hour PSI covers a whole day. Haze Now shows the 1-hour PM2.5 on the dial, and when the two readings point to different advice it gives the stricter one.

Haze usually eases when rain falls over the fires or the wind turns away. The 5-day forecast on each page says whether smoke is likely to keep drifting in and whether rain is likely, and where fires are the cause, when it may clear. It is a guide, not an official forecast.

In Singapore it uses NEA's five regions: North, South, East, West and Central. NEA publishes one reference point per region, not boundaries, so the site shows the region whose point is nearest to you. Tap any region to switch.

Everywhere else it uses the nearest air quality monitor that has reported in the last 3 hours, if there is one within 40 km. These are official and embassy monitors collected by the World Air Quality Index project (aqicn.org). With no monitor nearby, it shows a model estimate instead and says so.

In Singapore the big number is NEA's 1-hour PM2.5: fine particles in the air over the last hour, in micrograms per cubic metre. NEA calls it Normal up to 55, Elevated from 56 to 150, High from 151 to 250 and Very High above 250. The 24-hour PSI is Singapore's official index: up to 50 is Good, 51 to 100 Moderate, 101 to 200 Unhealthy, 201 to 300 Very Unhealthy and above 300 Hazardous.

Everywhere else the big number is the US Air Quality Index (AQI): up to 50 is Good, 51 to 100 Moderate, 101 to 150 Unhealthy for Sensitive Groups, 151 to 200 Unhealthy, 201 to 300 Very Unhealthy and above 300 Hazardous. Your country may publish its own scale, such as Malaysia's API or Indonesia's ISPU, and those numbers can differ.

The US scale is stricter than NEA's bands, so the same air can be Elevated on NEA's scale and Unhealthy on the US one. The US number shown for Singapore uses the US EPA table (2024) and the EPA's 12-hour NowCast. It does not change the advice.

Where there is no monitor nearby, the number is a model estimate. It covers the whole world but is coarse, and in smoke haze it can read much lower than the air you are breathing. If the air looks or smells worse, trust that and check your official source.

In Singapore the wording follows NEA's guide for 1-hour PM2.5 and the Ministry of Health's advisory for 24-hour PSI. When the two readings point to different advice, the site shows the stricter one and says which reading it came from.

Everywhere else it follows the US EPA's advice for each AQI level. The buttons under the advice switch between the advice for everyone and the advice for the more vulnerable: in Singapore NEA's "Vulnerable persons" (in NEA's words, "the elderly, pregnant women, children, and persons with chronic lung disease or heart disease"), elsewhere the EPA's "Sensitive groups" (children, older adults, pregnant people and people with heart or lung conditions).

The coloured days come from the Copernicus (CAMS) air quality forecast via Open-Meteo, scaled to match today's monitor readings because the model reads low in smoke haze. Whether smoke is drifting your way and whether rain is likely come from Google's experimental WeatherNext 3 weather model: the site traces where the air reaching you has been over the last four days and checks that path against fires seen by NASA satellites. Rain over those fires is what usually ends a haze episode.

It is updated every six hours. It is a guide, not an official forecast: check your national agency too. Google's terms do not allow its WeatherNext data to be used in some places. So the forecast is not shown to visitors in Indonesia, Japan, South Korea, Cuba, Iran or North Korea, or to visitors whose country cannot be told (for example over Tor). It is also not shown on the pages for places in those countries, such as Jakarta or Pekanbaru, wherever you are. Google's list also includes Crimea and the so-called Donetsk and Luhansk People's Republics; Haze Now has no pages there.

Singapore's readings come from NEA every hour. Monitor readings elsewhere are usually hourly too, and the site checks for new ones every 10 minutes. The 5-day forecast is updated every six hours. Each page shows when its reading was taken.