Haze has pushed air quality across Singapore into the unhealthy range. PM2.5 concentrations sit at elevated levels in all five regions of the island, which means the pollution is not confined to any one part of the city. Fine particles of that size settle deep in the lungs, so health authorities treat the readings as a reason for people to cut back on long spells outdoors. Those who work outside or exercise in the open are the most exposed groups. Smoky conditions of this kind typically arrive when fires burning elsewhere in the region send their smoke upwind, and shifts in wind direction decide which way the plume travels. Residents spent the day tracking real-time dashboards, waiting for the reading to retreat. If the haze holds, schools and outdoor events are the next adjustments to watch.