Mumbai: Mumbai’s air quality has begun deteriorating after the early withdrawal of the southwest monsoon, raising concerns that dry conditions and weaker winds could set the city up for a more polluted winter.

The India Meteorological Department began withdrawing the monsoon from Maharashtra on Saturday, October 3. The retreat came earlier than usual, while 21 districts in the state recorded deficient rainfall.

Mumbai’s Air Quality Index crossed 100 in early October, this post-monsoon season. Experts have linked the deterioration to declining rainfall, dry weather and changing wind patterns, which allow dust and pollutants from traffic, construction and other sources to remain suspended longer.

The city’s coastal location normally helps disperse pollutants, but weaker winds during the transition to winter could reduce that advantage. Dry air and dust transported from northern regions are also contributing to the haze.

Concern is heightened by an intensifying El Niño, which can alter atmospheric circulation and increase the likelihood of warmer and drier conditions. India’s 2026 monsoon ended with a 12.6 per cent rainfall deficit, according to the IMD.

Mumbai’s rainfall was uneven, with heavy showers in July offsetting deficits elsewhere in Maharashtra state. The Santacruz observatory recorded a 29 per cent deficit in June, a surplus of more than 55 per cent in July, and deficits of 35 per cent and 49 per cent in August and September.

With the dry season beginning, experts have called for tighter pollution monitoring, dust control and public-health advisories.