Pre-monsoon surprise: Mumbai's weather cools ahead of schedule

Dark clouds loom over Marine Drive on the evening of May 6. Pic/Shadab Khan

In a slight relief to Mumbaikars, the city is experiencing cooler-than-usual weather as mid-May approaches - a period typically known for intense heat and oppressive humidity. Surprisingly, current temperatures are milder than those recorded in March and April this year. Adding to the comfort, humidity levels have dropped slightly, according to meteorologists, offering further relief to residents used to sticky conditions during this time of year.

Experts say the pleasant shift in weather is due to the influence of a strong Western disturbance, which is triggering pre-monsoon activity across parts of the region. Light showers are expected over the coming days, contributing to the cooling trend and offering a much-needed reprieve ahead of the monsoon. On Tuesday, the India Meteorological Department's (IMD) Regional Meteorological Centre (RMC), Mumbai, issued a 'yellow alert' for Mumbai, Thane, Palghar, Raigad and other parts of Maharashtra, predicting thunderstorms and light rain.

In its latest Mumbai weather bulletin, the IMD stated that thunderstorms accompanied by lightning, light to moderate rainfall, and gusty winds (30 to 40 kmph) were very likely at isolated places. An orange alert has also been issued for Dhule, Nandurbar, Nashik, Pune and surrounding areas for the next two days, with a forecast of stronger thunderstorms and gusty winds (50 to 60 kmph).

"Mumbai's maximum temperatures are expected to hold steady around 34 degress Celsius , with minimums near 26 degrees - a welcome break from peak summer conditions. Between May 6 and 9, light showers are likely, though rainfall totals may remain under 10 mm. Some pockets in the MMR, especially Thane and Palghar, may see brief thunderstorms," said climatologist Rajesh Kapadia of the weather blog Vagaries of the Weather.

"In Pune, after days of 40 to 41-degree highs, a slight respite is expected with daytime temperatures dropping to around 38 degrees and lows to 22 degrees. Afternoon and evening clouds could bring localised thundershowers from May 6 to 8. North Konkan areas like Palghar and Dahanu, along with parts of Madhya Maharashtra including Nashik, Nandurbar, Dhule and Jalgaon, also stand a fair chance of pre-monsoon showers and thunderstorms during this period," he added.

Explaining the weather shift, Kapadia said: "A strong Western disturbance, marked by a southward-dipping trough in the subtropical jet stream, is persisting over Rajasthan and Gujarat, dropping south to 10°N over the Arabian Sea and drawing in a lot of moisture." Independent weather enthusiast Rushikesh Agre - known as Mumbai Rains on X - said, "This change is due to the southern shift of the Western disturbance affecting Gujarat and Rajasthan.

Since Mumbai is close to these states, northern Konkan, along with Mumbai, is also experiencing the same conditions. Days will remain cooler while nights may stay warm due to high humidity. Once rain begins around May 7, the humidity may ease. May 7 to 8 could bring good rain and some relief from the heat." Private weather agency Skymet Weather also indicated that Mumbai may see pre-monsoon showers earlier than usual this year - possibly before mid-May. "Pre-monsoon showers usually intensify after May 15, but this year is an outlier, with signs of early activity already emerging," Skymet stated.

According to Skymet, the northern plains have already seen significant thundershowers over recent days, with Rajasthan receiving substantial rainfall. A cyclonic circulation is now expected to move over central and southern Rajasthan and extend into northern Gujarat. At the same time, strong southwesterly winds will sweep across South Gujarat and the Konkan coast, pushing inland.

An anticyclone has also formed at the lower levels over the central Arabian Sea, near Goa and North Coastal Karnataka. "This is channelling moist northerly winds into Konkan and Goa, including Mumbai. Together, these systems are likely to trigger pre-monsoon showers in Mumbai ahead of schedule," the agency said.

Skymet meteorologists further explained that low-level winds over the Konkan region have largely shifted to southwesterlies. "This change has helped reduce land heating, keeping daytime temperatures steady between 33 degrees and 34 degrees at the Santacruz observatory. Minimums are likely to stay in the 24 to 26-degree range throughout the week. Light cloud cover is expected on May 6 and 7, with a slim chance of isolated showers. Widespread rain and thunderstorms are likely between May 8 and 11." However, Skymet clarified that the wet spell is unlikely to disrupt road, rail, or air transport operations during this time.