Haze threat Singapore Grand Prix on alert.

Since the inaugural Singapore Grand Prix in 2008, drivers have been routinely quizzed about how they would cope with a tropical downpour during the only Formula One race held entirely under floodlights.

After seven years of bone dry races, the answer still remains a mystery, but a different hazard could possibly threaten this year's race, scheduled for Sept. 20.

A dense cloud of haze has been hanging over the city-state of Singapore for the past week, a result of farmers in neighboring Sumatra burning forests to clear their land for agriculture.

An annual occurrence, the smog is currently rated under the Pollutant Standards Index (PSI) as being in the mid to low range of "unhealthy" air quality, but race organizers are monitoring the situation in case it worsens and effects driver visibility.

"The possibility of haze is just one of the many potential issues that are covered in the overall 2015 Formula 1 Singapore Airlines Singapore Grand Prix Contingency Plan," a Singapore GP spokesperson said in a statement to Reuters.

"The plan was formulated and refined with stake holders, government bodies and the Formula One community. 

"In the event that the haze caused visibility, public health or operational issues Singapore GP would work closely with the relevant agencies before making any collective decisions regarding the event."

A number of local sports events in Singapore were canceled this weekend because of health risks and the Singapore National Environment Agency told Reuters that the PSI levels were likely to remain in the "unhealthy" range for the next week.

"There has been a deterioration in the haze conditions in Singapore since early this morning, as the prevailing winds continued to blow in haze from Sumatra," the NEA said.

"As at 11 a.m. today, the 24-hr PSI was... in the low to mid sections of the unhealthy range."

Neither the NEA or race organizers would speculate on whether next Sunday's night race around the Marina Bay street circuit, could be effected if the smog worsened.

The Singapore Grand Prix is the 13th race of the season and defending world champion and last year's winner Lewis Hamilton will be a strong favorite to extend his championship lead, currently 53 points, with an eighth victory of the campaign.