Unseasonal downpour brings relief as Mumbai begins 2026 with cleaner air

Rainy morning in Sion. Pic/Atul Kamble

Mumbai started 2026 on a cleaner note as unseasonal drizzles swept parts of the city and neighbouring districts Thursday morning. The overall AQI stood at 90, in the ‘satisfactory' category, while the highest pollution readings were recorded at Deonar (110), BKC (105), and Colaba (104) - all in the ‘moderate' range.

In 2025, Mumbai recorded ‘satisfactory' air quality for nearly 40 per cent of the year, with January reporting all 31 days as ‘moderate'. Other months with a high number of satisfactory days included December (29), February (26), and November (24). The city logged just one ‘poor' day on October 11, when AQI spiked to 211 due to high ozone levels.

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The monsoon months - from May to September - brought clean air to the city, with all days recorded as green. December saw two green days: December 21 (AQI 91) and December 24 (AQI 86).

Concerns remain

Environmentalists caution that AQI numbers may hide persistent risks. Sumaira Abdulali, environmentalist and founder, Awaz Foundation, which has partnered with BMC for awareness and initiatives to curb noise and air pollution in the city, said, "PM2.5 levels in the air continue to be high. This is a major concern as PM2.5 poses severe health risks. The particles are so small that humans can inhale them, and they accumulate in the lungs, causing severe health problems. While the overall AQI may be low, high levels of PM2.5 concentrations in the air pose a severe problem."

Rare rain for city

Mumbaikars woke up to unpredicted showers between 6.30 am and 8.00 am on Thursday. Rushikesh Agre, a city based certified meteorologist from Harvard University said, "This phenomena is due to western disturbances originating in the Mediterranean sea. When these disturbances are weak, they move southward, resulting in rainfall."

How AQI is calculated

India's AQI considers eight major pollutants: PM10, PM2.5, carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), ammonia (NH3), and lead (Pb). Calculations require data from at least three pollutants, including PM10 or PM2.5.

PM2.5 trends

A CREA study found that for at least 35 per cent of 2025, every station in Mumbai reported PM2.5 levels above the city's annual mean of 34 µg/m³. Within the city, Deonar was the most polluted, followed by Worli and Bandra Kurla Complex (BKC), while Kandivli East recorded the most days exceeding the daily PM2.5 NAAQS in 2025.