Why monsoon arrival set to be unusual this year?

The southwest monsoon is expected to reach the Nicobar Islands around May 10 this year, nearly five days earlier than usual. The normal onset date for the monsoon over Nicobar is May 15, with the rest of the Andaman Islands typically covered by May 22.

Monsoon set to arrive early

This would make it a rare early onset. The last time the monsoon arrived this early was 17 years ago. In both 2007 and 2008, the monsoon reached the Nicobar Islands on May 10, according to India Meteorological Department (IMD) data.

Agriculture and crop scientist Athreya Shetty flagged this early trend in an independent forecast posted on X (formerly Twitter), calling it “a rare early onset.” Shetty regularly tracks weather patterns in the North Indian Ocean and points to this shift as significant for the region.

With #Monsoon2025 🌧️ set to arrive at #Nicobar islands in a little over a week, this would make it a rare early onset!

The last time this occured was 17 yrs ago! In 2007 & 2008 monsoon reached the Island chain on 10th May (Data IMD).

The Normal onset date over Nicobar is 15… https://t.co/8st0cPHSWT

— Athreya Shetty 🇮🇳 (@shetty_athreya) April 30, 2025

IMD has also forecast above-normal rainfall during the June to September monsoon season, pegged at 105% of the long-period average. It attributes this to favorable global conditions, including a weakening El Niño and a positive Indian Ocean Dipole (IOD). Low Himalayan and Eurasian snow cover during the past winter is another factor. These patterns often correlate with stronger and earlier monsoon winds.

Sea temperatures support rainfall

Several climatic factors contribute to this anticipated early onset. The IMD has noted that major drivers of the Indian monsoon, including the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), are currently in favorable phases. These conditions enhance the likelihood of an early and robust monsoon.

The snow cover over the Northern Hemisphere and Eurasia from January to March 2025 was below normal. Historically, reduced snow cover in these regions correlates with stronger monsoon activity over India

The early arrival of the monsoon is significant for several reasons. It allows for timely sowing of crops, which can lead to better yields and food security. Moreover, it aids in replenishing reservoirs and aquifers, ensuring adequate water supply for domestic and industrial use. However, while an early onset is beneficial, it also necessitates preparedness for potential flooding and other monsoon-related challenges.​

This year’s early signs show how much the monsoon still depends on both regional and global climate drivers. The next major update will come when IMD releases its second-stage forecast in late May, just before the monsoon reaches mainland India.

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