A strengthening El Niño climate pattern is expected to disrupt weather across Southeast Asia and South Asia in the coming months, raising the risk of drought, heatwaves and extreme rainfall, the United Nations warned on Friday, as Nepal prepared for what forecasters say could be a weaker-than-normal monsoon.

The World Meteorological Organization (WMO) said El Niño conditions had emerged in the tropical Pacific and were likely to strengthen rapidly into a strong event between July and September, increasing the chances of extreme weather across large parts of Asia and beyond.

While El Niño typically suppresses rainfall over much of South Asia, its impacts are more varied across Southeast Asia, where countries such as Indonesia, the Philippines, Thailand, Vietnam and parts of Malaysia often face prolonged dry spells, water shortages and heightened wildfire risks. At the same time, localized episodes of torrential rain and flooding remain possible where El Niño interacts with other climate systems.

"El Niño conditions are already underway and are forecast to strengthen rapidly into a strong event," WMO Secretary-General Celeste Saulo said in a statement.

"This will intensify the chances of drought and heavy rainfall and the risk of heatwaves on land and marine heatwaves in many regions of the world," she said.

The warning comes as governments across Southeast Asia monitor water supplies and agricultural production ahead of the region's main growing season, with rice-exporting nations particularly vulnerable to prolonged dry conditions. Previous strong El Niño events have reduced crop yields, strained hydropower generation and contributed to widespread forest fires in parts of maritime Southeast Asia.

In Nepal, the monsoon arrived later than usual, and the Department of Hydrology and Meteorology (DHM) has forecast below-average seasonal rainfall, heightening concerns over agriculture, drinking water supplies and hydropower generation.

"An El Niño year does not automatically mean a delayed monsoon or below-average rainfall," DHM spokesperson Bibhuti Pokharel told Everest Chronicle earlier.

"But rainfall often arrives later and remains below normal. This year, that tendency appears likely to be stronger," she said.

South Asia's summer monsoon provides roughly 70 percent of annual rainfall across much of the region and is critical for food production, particularly rice and maize. A weak monsoon can reduce harvests, lower river flows and increase food prices, while bursts of intense rainfall can still trigger deadly floods and landslides in Nepal and other Himalayan countries.

The WMO said it had stepped up climate information services and early warning support to help governments and humanitarian agencies prepare for the expected impacts.

Seasonal forecasts indicate sea surface temperatures in the central and eastern equatorial Pacific are likely to exceed two degrees Celsius above average between July and September, with El Niño expected to persist and strengthen through the Northern Hemisphere autumn.

The warning follows a WMO report showing global ocean temperatures reached a record high for June, partly driven by the developing El Niño.

Scientists caution that El Niño does not produce uniform impacts. Although much of South Asia faces an increased likelihood of below-average rainfall, Southeast Asia and the Himalayan region can still experience episodes of intense precipitation when El Niño combines with other climate drivers, reinforcing the need for robust forecasting and early warning systems.