New Delhi: Delhi's air quality deteriorated slightly on Monday, with the Air Quality Index (AQI) rising to 189 from Sunday's 167. Both readings fall within the 'moderate' category on the 0-500 AQI scale. The Centre's Air Quality Early Warning System (EWS) indicates that the air quality is likely to reach the 'poor' category by Tuesday. This would mark the first 'poor' air quality day in Delhi since June 11, when the AQI was recorded at 245. "Delhi's air quality is expected to remain in the 'poor' category from Oct 14 to 16," said officials. After this, AQI is expected to fluctuate between 'poor' and 'very poor', they said.According to Mahesh Palawat, vice president of Skymet Meteorology, the wind direction is westerly to northwesterly, and a marginal amount of stubble smoke is expected to drift in."We don't expect significant changes in terms of weather, with similar wind direction and low wind speed to persist," Palawat said. Data from IITM's Decision Support System (DSS) indicates that stubble burning contributed only about 0.62% to Delhi's PM2.5 levels on Monday, a slight increase from 0.24% on Sunday. DSS projects a 0.49% contribution from stubble burning on Tuesday. The largest sources of pollution remain Delhi's transport sector (19.6%), followed by Jhajjar (9.8%) and Sonipat (6.1%). Monday's maximum temperature reached 32.6°C. City will see a rise in temperature to around 34°C by Wednesday. TNN