By 2030s, Mumbai could see 1°C rise in temperatures, 6-7 more heavy rain days: New climate projections

Mumbai: Mumbai could see average temperatures rise by 1°C and an additional six to seven days of heavy rain by the 2030s, according to new climate projections released Friday by Bengaluru’s Azim Premji University.

The projections analyse climate conditions along India’s coastline for 2021–2040 compared with a 1960s baseline, under different global warming scenarios.

Given that it is already 2026, “some of these changes are already beginning to emerge”, said Santonu Goswami, professor at the School of Climate Change & Sustainability at Azim Premji University.

For Mumbai, the projections suggest minimum temperatures could rise faster than daytime highs — something other studies also indicate. Winter minimum temperatures are expected to increase the most — by as much as 1.3°C in the coming decade under a moderate global warming scenario.

Wet-bulb temperatures—which combine heat and humidity and are closely linked to heat stress on the human body—are also projected to rise steadily increasing by around 1.3°C over the 2021-2040 period. Average humidity is also expected to increase.

Mumbai could also see close to two days over 40°C by the late 2030s — temperatures that are almost unheard of in the city.

Overall summer maximum temperatures are projected to rise by around 0.9°C, the study found. Among coastal districts, Ernakulam in Kerala is projected to see the sharpest increase at 1.3°C.

In terms of the southwest monsoon, the study projects an increase of roughly 300–350 mm in annual rainfall across Mumbai city and suburbs, and around a week more of heavy and very heavy rain days each year.

Cities like Mumbai must plan for these conditions, Goswami said, adding that district-wide averages often obscure neighbourhood-level differences. For instance, “It’s much cooler under some trees” than on open roads, he noted.