'No clear indications' of El Nino, La Nina — what that means for summer, Southwest Monsoon of 2025 

According to the Japan’s weather bureau, “There were no clear indications of El Nino or La Nina events, although La Nina characteristics were becoming evident.”

“There is a 60 per cent likelihood of an ordinary weather pattern continuing towards the summer,” news agencies quoted the Japanese weather bureau as saying this Monday.

The World Meteorological Organisation has already predicted the “return of the ENSO-neutral conditions during February-April 2025”. “Latest forecasts from WMO Global Producing Centres of Long-Range Forecasts indicate a 55-per cent likelihood of a transition from the current neutral conditions (neither El Nino nor La Nina) to La Nina conditions during December 2024 to February 2025. The return of the ENSO-neutral conditions is then favoured during February-April 2025, with about 55 per cent chance,” the WMO stated in December 2024. 

Basically, some La Nina characteristics seem to be emerging.

El Nino-La Nina — what they mean

El Nino is a warming of ocean surface temperatures in the eastern and central Pacific Ocean. La Nina refers to the large-scale cooling of the sea surface temperatures (SSTs) in the central and eastern Pacific Ocean. Both are coupled with changes in the tropical atmospheric circulation like winds, pressure and rainfall.

Generally, a La Nina event produces opposite large-scale climate impacts to an El Nino event, especially in tropical regions. However, climate change is becoming a concern. It is expected to increase the frequency and intensity of both La Nina and El Nino events due to a likely rise in the ocean and atmospheric temperatures.

 What does it mean for India?

El Nino and La Nina both influence global weather patterns. They also have a direct effect on the Southwest Monsoon — the lifeline of India, its agriculture, water resources, economy and general well-being.

Mostly during an El Nino event, the June-September rains are weaker than normal. The intensity of the event also decides the amount of impact it has on seasonal rains that year, says the IMD.

Since 1950, there have been 16 El Nino years. Of these, seven years impacted Indian monsoon with below-normal rainfall. 

There also exists a stronger inverse relationship between El Nino and rainfall during the latter half of the four-month season, particularly with September rainfall, according to the weather office.

Impact on summer and Southwest Monsoon

La Nina, the climate phenomenon characterised by notably cooler SSTs, is the opposite of El Nino.

This part of El Nino Southern Oscillation (ENSO) is characterised by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Nino, which is characterised by unusually warm ocean temperatures in the Equatorial Pacific.

Generally, during a La Nina event, normal to above-normal rainfall is received over India during the June-September season. Most parts receive above-normal rainfall during the La Nina years, except extreme North India and some areas over Northeast India. These regions can expect below-normal rains during La Nina years. Below-normal temperatures are also observed during the winter season during La Nina years, as per the IMD.

The last time La Nina occurred was from 2020 to 2023 when normal to above-normal rains were witnessed across most parts of the country during monsoon. In some parts, there were floods and damage to crops.

La Nina was expected to occur in July last year.

Weather experts say the chances of developing La Nina are around 55 to 60 per cent. This may impact the intensity and timing of rains, and perhaps also the temperatures during the summer. If La Nina sets in early in 2025, it may result in a strong monsoon season, they add.