Some outdoor activities in Singapore were postponed following the haze. It was a concern in the week leading up to the 2015 Singapore Grand Prix as the event could have come under threat of haze. The haze rose into the "very unhealthy" range of the Pollutant Standards Index on 14 September, with a reading of 223 at 8 p.m. It rose further to 249 at 9 p.m. before dropping back to the "unhealthy" range for the rest of the night. Thunderstorms and rain had improved the situation in the afternoons of the 15th and 16th, while a change in prevailing wind direction improved the situation from the 20th to the 22nd.