Raging blazes in Indonesia have been spewing toxic haze over neighbouring Singapore and Malaysia, with Jakarta deploying tens of thousands of personnel and water-bombing aircraft to tackle them.
The Indonesian fires are an annual problem during the dry season when farmers use illegal slash-and-burn techniques to clear land for agriculture, but this year's are the worst since 2015.
Thick smog had been hanging over Singapore since last weekend, pushing air quality to unhealthy levels, obscuring the waterfront skyline and sparking fears that Sunday's showpiece F1 night race may be knocked off track.
But on Friday the skies were largely clear, with only a light haze over the city, while air quality improved to a "moderate" level of around 60 on the National Environment Agency's scale.
A reading between 101 and 200 indicates unhealthy air quality.
The wind direction could however still change ahead of the weekend and push smog back over Singapore.
F1 organisers say they have a contingency plan if the haze worsens and have been stocking up on face masks to protect against pollution which spectators can buy at the circuit.
Indonesia and Malaysia have been worst affected by haze from the fires, which are burning on Indonesia's Sumatra island and the Indonesian part of Borneo. Borneo is shared between Indonesia, Malaysia and Brunei.
Thousands of schools have been forced to close in both countries amid mounting health concerns, while several airports have shut in Indonesian Borneo due to poor visibility.
People have been dashing to buy face masks in affected areas and there has been an increase in reports of respiratory illnesses and conditions such as dry and itchy eyes.
On Friday more than 2,600 schools were closed in Malaysia, education authorities said.
The worst-affected state was Sarawak, on Borneo, where more than 1,000 schools were shuttered and air quality reached "hazardous" levels in one area bordering Indonesia, according to an official index.