Southwest monsoon likely to reach Kerala on May 26, says IMD

This year, the Southwest monsoon is likely to reach Kerala on May 26, the India Meteorological Department (IMD) predicted. In a press release on Friday, May 15, the IMD said, “This year, the southwest monsoon is likely to set in over Kerala on 26th May with a model error of ± 4 days.”

According to the IMD, the Southwest monsoon normally sets in over Kerala on June 1, with a standard deviation of about seven days.

How accurate are IMD's predictions?

The monsoon hit Kerala last year on May 24, marking an early onset, eight days ahead of the normal June 1 date. The IMD, however, had predicted May 27 as the arrival date of the Southwest Monsoon.

IMD said its operational forecasts of the date of monsoon onset over Kerala during the past 21 years (2005-2025) “proved to be correct except in 2015.”

The weather department also shared “forecast verification” for the recent 6 years (2020-2025), which is given in the table below.

The Department of Energy and Environment says the season usually begins in early June when the monsoon winds reach Kerala. Over the next few weeks, these winds spread across the entire country. By mid-July, most of India is covered.

Why is Southwest Monsoon arrival in Kerala important?

The IMD explains that the advance of the southwest monsoon over the Indian mainland is marked by monsoon onset over Kerala.

It is an important indicator that characterises the transition from the hot and dry season to the rainy season.

Monsoon rains are critical for the agricultural sector, with productivity and food grain prices closely linked to a good monsoon, the government said in a press release last year. They are crucial for replenishing the country’s water reserves, and for the generation of hydroelectricity.

The southwest monsoon is India’s main rainy season and “a lifeline for the country’s economy and ecology.” It supports farming, fills rivers and lakes, and recharges groundwater.

About 75 per cent of India’s total rainfall occurs during this season, making it essential for irrigation, drinking water, and even hydropower electricity generation.

The El Niño Effect

Several reports claim that this year, the world could see a "strong" El Niño, a natural climate event that forms in the Pacific Ocean and influences weather patterns worldwide, including in India.

NOAA’s Climate Prediction Center said in its 14 May report that there is an 82 percent chance of an El Niño arriving between May and July and a 96 percent chance of it developing by December. Right now, it could be too early to say how strong this El Niño will be, even as several reports hint at a “very strong event.”

During an El Niño year, the usual flow of moist winds towards India is disrupted. This change reduces the amount of rainfall India receives between June and September.

In the past, strong El Niño events have led to significant rainfall declines, late monsoon arrival, and dry spells in key agricultural states.