Singaporeans headed indoors to seek respite from the hazardous haze last night, as evident in the visibly thinner crowds in popular shopping and dining areas like Orchard Road, Clarke Quay and Boat Quay.
Many people wore masks and used handkerchiefs and tissue to cover their mouths, while others were seen scurrying indoors.
Pub and restaurant staff at Clarke Quay and Boat Quay said customers have been staying away since Monday, but last night was the quietest of the week so far.
Mr Yap Eng Chew, who owns Harvest Seafood at Boat Quay, said business had halved yesterday. "Usually, I would be able to get passers-by to come for dinner at my restaurant but today, there are few people here," he said.
It was the same story a few doors away at Italian restaurant Pasta Fresca Da Salvatore. Only one table in the outdoor area was occupied.
Waiter Aung Khin Myint said: "Our customers said they want to sit indoors because their eyes and throats were irritated."
Mr Ryan Ravelo, manager of Senor Taco at Clarke Quay, added: "We are usually full almost every night. But today, only three out of our seven tables are full. Even our regulars are staying away."
Some shoppers and diners said they were going home early because they had difficulty breathing, or their eyes were watering.
Ms Sarah Emmanuel, 24, who works for an events and public relations company, said: "It is really bad. Even in the underground tunnels in Orchard Road, you can smell the smoke."
Software engineer Dilpreet Singh, 32, shelved dinner plans at Boat Quay and bought a meal to eat in his office.
"I am buying dinner for eight of my colleagues too because no one wants to come out. The air quality is so bad," he said.
IT engineer Kuo Ting Ting and her friend Ray Zhang usually dine at Boat Quay after going to the gym, but decided to go home instead.
Said Ms Kuo, 29: "We usually have dinner here along the Singapore River to unwind. But we are going home as soon as possible today. We don't want our health to be affected."
The heartlands appeared to be less affected. Shopping areas such as Junction 8 in Bishan were still packed with shoppers and diners.
Twins Jane and Jenny Goh, 18, were among those who sat outside The Coffee Bean & Tea Leaf cafe at Junction 8. They had heard that the PSI had hit 290 at the time, but shrugged it off.
Jane, a student at the Millennia Institute, said: "It is quite hot out here, but there were no seats inside earlier, and now we are too lazy to move."
Marketing communications manager Wendy Ong, 27, was more cautious. She said she immediately closed all the windows in her house after learning about the PSI levels on the news on television.
Bishan Swimming Complex was almost empty. A lifeguard who gave her name only as Marian said there had been only 10 swimmers all day. Staff at the outdoor pool have been advising visitors of the PSI reading this week and telling them to go home.
Even the ongoing National Day Parade rehearsals could fall victim to the haze.
Parade and ceremony chairman, Senior Lieutenant-Colonel Simon Lee, told The Straits Times yesterday that the executive committee was discussing contingency plans in case the haze worsens.
"It could be a scenario that the schoolchildren are not involved, so we are left with the adults. Another scenario could be that we truncate the parade and make it shorter," he said.
Additional reporting by Jermyn Chow