The haze cast a cloud over public holiday plans yesterday as people stayed indoors due to the poor air quality.
Food and beverage businesses were also affected and some country clubs closed their golf courses.
Events manager Winnie Lin, 32, who is 32 weeks pregnant, was unable to walk her dog because of the haze. "I went out in the morning for breakfast but found it very hard to breathe so I'm going to stay indoors and avoid going out," she said.
Auditor Annabel Loh, 26, said: "I planned to do a hike at 5am at MacRitchie Reservoir to prepare for my Bali trekking trip next month. I would have continued while wearing a mask if the PSI was below 200. However, I had to cancel it."
Mr Eric Lim, 32, went ahead with shopping plans with his wife "to hide indoors in the malls". The corporate communications executive said: "We didn't bring our one- year-old son out. He's staying home with the air-con and air purifier on."
While the pollution did not put a stop to the Korban rituals - which marked Hari Raya Haji - across the island, volunteers at participating mosques were given N95 masks.
Some families were put off making Hari Raya Haji visits to friends and relatives. Preschool teacher Juriana Juhari, 32, said: "My 11-month-old daughter has asthma so we had to stay indoors. We went to the mosque in the morning and went straight home. I wanted to go visiting but decided not to."
Teacher Yati Isnin, 33, who wore a mask outside, added: "We cut down our visits from five to two houses."
Outdoor businesses hoping for a windfall on the public holiday were also disappointed.
Mr Juwanda Hashim, owner of the Fabulous Baker Boy cafe at Fort Canning Hill, said business has fallen by around 30 to 40 per cent over the past three weeks due to the haze.
Mr Seth Kho, manager of Riders Cafe in Bukit Timah, said more than half of its 168 brunch customers cancelled reservations yesterday. "It's really quiet for a public holiday," he said. "We are really affected because of the haze. We have no air-conditioning... We thought it got better last week but suddenly now, it's worse."
It was the same for beachfront Italian eatery Trapizza at Siloso Beach on Sentosa. Supervisor Dioa Jovolin said: "We usually see at least half the restaurant filled on weekends and public holidays, but the haze was so terrible today that we only got three tables of customers."
At electric karting track The Karting Arena, which opened this week at Turf City, fewer people than expected turned up. Owner Yuey Tan said: "It's unfortunate that the haze has worsened in the past few days, but what's important is to stay healthy during this period."
Singapore Island Country Club closed its three golf courses at 6.30am, as well as its outdoor area.
Raffles Country Club closed its two golf courses. "We had some members play in the morning, but because of the situation, we decided to close the golf courses. Reservations were also cancelled," said its operations executive Joeness Lamban. "Usually on a public holiday, or weekends, golf courses are more crowded but we had no choice but to close it."
Some outdoor workers remained on duty despite the haze.
Ramky Cleantech Services director Milton Ng said his cleaners working in exposed areas had been issued masks. "We are asked to scale down on certain operations like desilting of drains if the 24-hour PSI goes above 250, but litter bin clearance and mechanical road sweeping still continue," he said. "Singaporeans still litter regardless of the haze."
•Additional reporting by Joanna Seow, Kok Xing Hui and Lee Min Kok