Major setback before Diwali, Delhi's air quality to enter 'severe' category

The week of Diwali presents a troubling forecast, with air quality likely to fluctuate between "very poor" and "severe" categories due to adverse meteorological conditions.

In Short

• Delhi air quality to enter 'Very Poor' category by October 26-27
• Diwali week forecast shows 'Very Poor' to 'Severe' air quality
• Wind speeds to weaken, affecting pollutant levels

As Diwali nears, Delhi’s air quality is set to decline significantly, with levels expected to enter the "very poor" category over the weekend, starting October 26-27. While recent high wind speeds and favourable ventilation have briefly eased pollution in the city, the air quality had already fallen into the "poor" range by Friday.

The week of Diwali presents a troubling forecast, with air quality likely to fluctuate between "very poor" and "severe" categories due to adverse meteorological conditions. Calm nighttime winds are expected to hinder pollutant dispersion, increasing health risks for Delhi residents as pollutant concentrations intensify.

Surface wind conditions will also influence pollution levels. On October 24, winds were recorded at 8-16 kmph from the West/Northwest, but are forecasted to shift and weaken over the following days. October 25 brings a shift to Northwest/Northeast winds at 4-18 kmph, followed by North/Southeast winds at 4-8 kmph on October 26, and Southeast winds at 10-12 kmph on October 27.

The pollutant mixing depth will range from 1200 to 1500 meters, with the ventilation index, which gauges atmospheric dispersal capacity, remaining below the optimal 6000 m²/s threshold on multiple days. Combined with average wind speeds under 10 kmph, these stagnant conditions are likely to exacerbate Delhi’s air pollution just as Diwali festivities commence.