On Thursday night local time the Ministry of Education said it would close primary and secondary schools on Friday, along with government-run kindergartens, after the Pollutant Standards Index (PSI) reading, which measures how polluted the air is, hit 314 and the 24-hour figure rose to 223-275 at 10pm local time on Thursday. Anything over 300 indicates "hazardous" air quality and 201-300 is "very unhealthy", Singapore's National Environment Agency said on its website.
Not all schools have air conditioning fitted, preventing them from closing windows to shut out the smoky air.
On Friday the PSI hovered near the hazardous range again, hitting 255, with the 24-hour figure at 264-321.
Slash-and-burn agriculture, and resulting forest fires, in Indonesia's Sumatra and Kalimantan islands are responsible for the so-called haze that hangs over Singapore. Indonesia and parts of Malaysia are also affected, with PSI readings in Kalimantan nearing 2,000, according to reports.
Although Singapore offices remained open on Friday, Prime Minister Lee Hsien Loong took to Facebook to urge employers to "not compromise on the health and safety of their employees, especially those working outdoors."
Singapore's residents, meanwhile, were growing weary of the yellow smog clouding the city's skies; people with thick surgical masks covering half of their face are currently a common sight in the city-state.
"It's getting worse now," Jabbar Hanieff told CNBC on Friday. "It's affecting everybody, especially people like me. But to use the cup (mask), every time you have to take it out when you go in, it's creating a lot of problems. So I hope this thing will go off as soon as possible."
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The effects of the haze are worst for those with breathing-related conditions. Toh Shu Hui said: "You can see it's affecting my daily life. I get respiratory problems, sinus. It's very common [and] it's affecting my family as well."
Some residents did see a lighter side to the problem. Local Twitter celebrity mrbrown, who started the hashtage #sghazesongs, was inundated with suggestions, from The Platters' Smoke Gets in Your Eyes to Deep Purple's Smoke on the Water and Billy Joel's We Didn't Start the Fire and No Air by Chris Brown and Jordin Sparks.
But outdoor pursuits have largely ground to a halt during the haze, which started earlier this month.
The Singapore Sports Hub said on its website that it would suspend all outdoor activities at its stadium and aquatic complex. Health advisories sent out by the Ministry of Health and the National Environment Agency urged residents to minimize time spent outside.
And fast food restaurants including KFC and McDonalds have suspended their delivery services to protect workers from the smog.
Indonesia is investigating about 100 companies for their alleged links to the forest fires and recently ordered four to suspend their operations, Reuters reported. Officials hope to extinguish the majority of the fires by mid-October.
Reports suggest, however, that the El Nino phenomenon, which results in very dry weather, means the haze could continue until the monsoon season begins in November.