The skies were slightly hazier than usual on Monday.
The three-hour PSI or Pollutant Standards Index, a measure of air quality, began creeping up on Sunday afternoon, and was 50 at lunchtime on Monday. At 6pm, the three-hour PSI was 38, while the 24-hour PSI was 44 to 49.
A PSI of 0 to 50 remains in the 'good' range, while that between 51 and 100 is 'moderate'.
The National Environment Agency (NEA) said the conditions were due to dust blowing from the north and northeast.
Northern Asean and East Asia had been experiencing dry conditions for the past few weeks, an NEA spokesman said.
Air quality is expected to improve with showers over the next few days, she added.
The agency said it was monitoring the situation closely and would provide further updates when necessary.