Will rainfall be below normal in India this season? Is it a matter of concern?

The southwest monsoon officially arrived over Kerala on June 4, marking the start of India’s rainfall season. But even before the rains set in, the India Meteorological Department (IMD) revised its forecast for the 2026 monsoon.

In its updated long-range forecast, the weather office said the country is likely to receive seasonal rainfall equivalent to 90 per cent of the Long Period Average (LPA) during the June-September monsoon, with a model error margin of ±4 per cent. The forecast marks a slight downward revision from the 92 per cent estimate issued earlier this year.

“Quantitatively, the southwest monsoon rainfall over the country as a whole is likely to be 90 per cent of the long-period average. Earlier, we had said it would be 92 per cent, but now it has been reduced to 90 per cent … rainfall will be below normal across the country as a whole,” said M Ravichandran, secretary, Ministry of Earth Sciences, during a press conference.

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The announcement immediately raised questions. What exactly does 90 per cent of the LPA mean? Will every state receive 10 per cent less rain than usual? Does a below-normal monsoon automatically mean drought?

The short answer is no.

Rainfall is expected to be below normal across the country this year. Vinayaraj via Wikimedia Commons

How to read rainfall

The LPA is India’s average monsoon rainfall over a long historical period (1971-2020). For the June-September monsoon season, that number is 87 cm. When the IMD says rainfall is likely to be 90 per cent of the LPA, it means India as a whole is expected to receive slightly less monsoon rainfall than its long-term average.

But that does not mean every part of India will get 10 per cent less rain. Rainfall varies enormously across the country, and even neighbouring districts can experience very different monsoon patterns.

“Usually, everyone expects similar rainfall in their locations, but one also needs to look at hyperlocal variability and the regional factors that can even reduce or increase the seasonal quantum on either side of the forecast,” explained Athreya Shetty, independent weather forecaster. “We are a vast country with a plethora of microclimatic variations, so significant deviations are a given.”

This is already reflected in the IMD’s outlook. Northeast India is expected to receive normal rainfall, while central India, northwest India and much of the south peninsula are likely to record below-normal rainfall. The department has also warned that rainfall over the monsoon core zone, a crucial agricultural belt for kharif crops, is likely to remain below normal.

Rainfall is expected to be normal in Northeast India. Wann Majaw via Wikimedia Commons

What does ‘deficient’ rain mean?

The forecast categories can also be confusing. Rainfall between 96 per cent and 104 per cent of the LPA is considered normal. Rainfall between 90 per cent and 95 per cent falls in the below-normal category, while anything below 90 per cent is classified as deficient. At 90 per cent of the LPA, the forecast sits exactly at the threshold between the below-normal and deficient categories.

The department has also said there is a 60 per cent probability of a deficient southwest monsoon season. In other words, while the central forecast remains 90 per cent of the LPA, weather models indicate a significant chance that seasonal rainfall could ultimately fall below the 90 per cent threshold that marks a deficient monsoon.

A farm worker carrying fodder walks in a dried paddy field on the outskirts of Ahmedabad. A below-normal monsoon also does not automatically mean a drought year for the full country. File photo/Reuters

“While below normal indicates that rainfall will be less than the normal average, it still is the safe zone and may not cause too much impact. Deficient starts entering the territory to be concerned, where the expected rainfall falls below 90 per cent and in worst cases, can lead to drought conditions for a few regions that already receive less rain,” said Shetty.

A below-normal monsoon also does not automatically mean a drought year for the full country. India has experienced below-normal monsoons in the past without widespread drought. The impact depends on several factors, including where rainfall deficits occur, how rainfall is distributed throughout the season, reservoir storage levels, and local water availability. A season with below-average rainfall nationally can still bring adequate rain to many regions. On the other hand, rainfall concentrated in a few intense spells can create a different set of challenges.

This is why meteorologists caution against placing too much emphasis on a single seasonal forecast. The southwest monsoon lasts four months, and conditions can change considerably during that period. Ocean temperatures, atmospheric circulation patterns and regional weather systems continue to evolve as the season progresses.

The IMD therefore supplements its seasonal forecast with monthly outlooks, weekly rainfall assessments, and forecasts for major rainfall events. “Keeping up to date with IMD seasonal forecasts, monthly outlooks and any major rainfall event will give an idea,” said Shetty.

Weekly rainfall reports can reveal whether the monsoon is entering an active phase, when rainfall becomes widespread, or a break phase, when rainfall temporarily weakens. For farmers, policy makers and the public, these shorter-term updates are often more useful than the seasonal forecast.