MUMBAI: Brace for unseasonal rainfall this weekend as the India Meteorological Department (IMD) on Wednesday issued a 'yellow' alert for Mumbai, Thane and Palghar indicating thunderstorms accompanied with lightning and gusty winds (30-40 kmph) at one or two places being very likely.

The rain is likely to further improve the city's air quality.

The Air Quality Index (AQI) on Wednesday was 122, which is in the 'moderate' category, according to data from the System of Air Quality and Weather Forecasting and Research.IMD officials said a trough has formed in the Bay of Bengal coast due to which rainfall activities are expected in the city and adjoining areas."This trough is moving towards the Maharashtra coastline, which may lead to rainfall in several coastal districts, including parts of the Mumbai metropolitan region," said officials.

Earlier, on November 9, many pockets in the city, including Mulund, Malad and Goregaon, as well as Kalyan, Dombivli, Thane and parts of Navi Mumbai had received a brief speall of heavy rainfall.