Parents had to make alternative plans for their children last night as the haze caused primary and secondary schools around the island to be closed.
Video producer Melvyn Goh said his two daughters, who are both in primary school, will stay at home with their helper.
"Thankfully that's settled, because my wife is overseas, so if we didn't have a helper I might have had to cancel my video shoot to look after them," said the 39-year-old.
"My Primary 1 daughter is happy there's no school, but the Primary 4 one said she was 'bummed out' about it because there was a netball competition she was looking forward to."
The Ministry of Education (MOE) had prepared for such an eventuality and is keeping schools open for students who turn up, with supervisors on hand to look after them in libraries and other rooms. National examinations scheduled for today have also been postponed.
More than 100 students who were due to take the GCE O-level Music and Higher Music practical exams today will take them at 8am next Tuesday instead.
They were notified of the rescheduling by their schools yesterday while private candidates were informed by the exam board.
Minister for the Environment and Water Resources Vivian Balakrishnan said at a media briefing last night that there has been a general upward trend in the hourly raw concentration of PM2.5 particles, which affects the Pollutant Standards Index (PSI).
There was a brief respite over last weekend and early this week as the winds were blowing from the south and south-east.
The haze returned in force on Wednesday due to a change in wind direction because of a tropical storm in the western Pacific Ocean, east of the Philippines.
The storm acts as a "low-pressure zone", said Dr Balakrishnan. That causes wind to blow from the south or south-west, sending haze from a dense haze cloud sitting slightly to the south of Singapore into the nation.
Contingency plans for national examinations are in place should haze conditions remain unhealthy or worsen. All schools have enclosed spaces for candidates to take their exams, and schools will also be provided with air purifiers so that exams are not disrupted.
"We will certainly announce our plans if we need. This is a very fast-moving situation, but we are prepared," said Education Minister Heng Swee Keat. Should the air quality enter the hazardous level resulting in further school closures, exams will be rescheduled.
Some companies possibly responsible for the haze have been identified, Dr Balakrishnan added.
The Transboundary Haze Pollution Act punishes polluters who cause haze. They can be fined up to $100,000 per day, capped at a total of $2 million.
Dr Balakrishnan said: "The National Environment Agency has written to the Indonesian authorities, asking for a list of companies whom the Indonesian investigations have shown may be implicated in this. Pursuant to our Transboundary Haze Pollution Act, we will be issuing notices in the days to come."