MUMBAI: Mumbai is witnessing an unusually early spell of pre-monsoon showers this May, a rarity according to independent weather experts.

With the city's average May rainfall typically just 12 mm, such widespread rain this early in the month caught many by surprise.

"It's unusual for Mumbai to see pre-monsoon activities from early May like what we saw on May 7-8 this year.

With the monthly average being just 12 mm, usually, the city only sees stray showers towards the end of May, which is also not a guarantee every year," said independent forecaster Athreya Shetty.Shetty also points out how the current pre-monsoon activity already pushed rainfall totals close to 50 mm — levels not seen since the early 2000s, if one discounts the exceptional 2021 year spell brought on by Cyclone Tauktae, which was 230 mm.

Rainfall recorded this year since March 1 by the IMD Colaba and Santacruz conservatory was 62.8 mm and 38.4 mm, of which a majority was recorded this month itself.This current surge in pre-monsoon showers also raised hopes of an early monsoon arrival. The India Meteorological Department (IMD) indicated that the southwest monsoon is expected to hit Kerala around May 27, with a model error of four days. A few independent forecasters believe this could mean an early onset in Mumbai as well—possibly around the first few days of the month instead of the usual June 11 date.

Rushikesh Agre, who tracks Mumbai weather and regularly posts on it from his social media handle on X and Instagram, said that monsoon onset over Mumbai is likely around June 5–7, 2025. "Based on current indicators, its progression is expected to accelerate over the next 4–5 days, with strong activity expected over the following two weeks," he said.Rajesh Kapadia, who runs the private weather blog Vagaries of the Weather, also agreed that this year's pre-monsoon activity arrived earlier than usual. "Heat isn't making headlines this peak summer. Instead, there's ample moisture and frequent thunderstorm buildup—conditions that point to a likely early onset of the monsoon in Mumbai," Kapadia said.The IMD, meanwhile, placed Mumbai under a light to moderate rainfall warning until June 20, 2025, suggesting the city could continue to see frequent showers in the days leading up to the monsoon's formal arrival.