The haze is back! 3-hour PSI briefly crosses into unhealthy range

Singapore was shrouded by haze on Wednesday, with the three-hour Pollutant Standards Index (PSI) reading briefly creeping into the unhealthy range.

The three-hour PSI reading was 55 at 7am but continued to inch up throughout the day, hitting a high of 102 at 8pm. The reading then dropped to 94 at 11pm.

Time 7am 8am 9am 10am 11am 12pm 1pm 2pm
3-hr PSI 55 56 57 59 59 60 60 58
Time 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm
3-hr PSI 60 65 75 86 93 102 100 99 94

A reading between 51 and 100 is considered moderate. A reading between 101 and 200 is considered unhealthy.

PSI Value Air Quality Descriptor
0-50 Good
51-100 Moderate
101-200 Unhealthy
201-300 Very unhealthy
Above 300 Hazardous

The National Environment Agency (NEA) said in its daily haze advisory that the haze was likely due to smoke blown into the country by prevailing winds.

Only 23 hotspots were detected in Sumatra, Indonesia, on Wednesday, though this was likely due to cloud cover over parts of the island.

Meanwhile, 139 hotspots were detected in Kalimantan, Indonesia.

Conditions could improve on Thursday with rain expected in the late morning and early afternoon.

"The overall air quality for the next 24 hours is expected to be in the high-end of the moderate range but may creep into the low end of the unhealthy range from time to time," NEA said.

To find out the PSI reading, click here.