The National Environment Agency (NEA) has dismissed rumours via SMS on cloud seeding to mitigate the impact of the haze on this weekend's Formula 1 (F1) race.

In a statement, the NEA said it was aware that there was an SMS rumour being circulated suggesting that the government was conducting cloud seeding to mitigate the impact of the haze on F1, and that the resultant rain from this was harmful.

"These claims are untrue," it said.

The NEA said the government had not been conducting cloud seeding and had no plans to do so.

Cloud seeding attempts to artificially induce rain by implanting clouds with suitable particles.

However, the NEA said there were no reliable means to validate the effectiveness of cloud seeding in Singapore.

It explained that cloud seeding also required existing clouds as it could not generate rain out of thin and dry air.

"During dry seasons, cloud seeding is less effective due to the lack of suitable clouds for seeding.

"The small size of Singapore and the variability of winds also mean that the induced rain, if any, may not fall directly over our island," it said.

For official and authoritative information, the public is advised to refer to the NEA website (www.nea.gov.sg), the haze microsite (www.haze.gov.sg) or follow it on the NEA Facebook (www.facebook.com/NEASingapore) and NEA Twitter (@NEAsg), or download the myENV app.

Meanwhile, there has been improvement in air quality in Singapore today.

As at 10am today, the 24-hr PSI was 79-99, in the moderate range, and the 3-hr PSI was 64.