Monsoon Brings Average Rainfall Despite El Niño Effects; What to Expect This Winter Season?

Though the developing El Niño system in the Pacific Ocean was expected to cause below-average rainfall during this year’s monsoon, recent data from Nepal’s Department of Hydrology and Meteorology (DHM) indicate nearly average rainfall across the country. Prior to the monsoon onset, forecasts predicted rising temperatures and reduced precipitation due to El Niño’s influence. From June 19 to September 30, Nepal recorded roughly 1,326 millimeters of rainfall, compared to the average monsoon precipitation of about 1,500 millimeters. Generally, monsoon rainfall between 90 to 110 percent of the average is considered normal. According to meteorologist Ashok Bakharel from the DHM, preliminary studies show approximately 95 percent rainfall as of the first week of October. This year’s monsoon arrived about six days late, starting on June 19. The DHM notes that the monsoon is yet to withdraw fully from central and eastern parts of Nepal.

Regarding regional variations, meteorologist Rojen Lamichhane reports that while the Madhesh Province experienced below-average rainfall overall, some locations saw above-average precipitation. “Preliminary figures indicate reduced rainfall in Madhesh Province, but areas around Kathmandu and Sindhupalchok in Bagmati Province and parts of Gandaki Province received higher-than-normal rainfall. Comprehensive data is still pending,” Lamichhane said. According to figures up to late September, rainfall measurement stations in Dhangadhi, Birendranagar, Lumle, Nepalgunj Airport, Janakpur, Biratnagar, Dhankuta, and Dharan reported below-average rainfall. Conversely, stations such as Jumla, Jomsom, and Kathmandu Airport recorded above-average precipitation, as reflected in the department’s monsoon rainfall monitoring data. The DHM further reported that starting from October 3, the monsoon began retreating in parts of Sudurpashchim Province, Karnali, and western areas of Lumbini and Gandaki Provinces, while withdrawal continues in other regions. Meanwhile, westerly winds and local weather systems have brought rain to many parts of Nepal. “Although rainfall may cause flooding in rivers, the monsoon itself has weakened. The influence of the western low-pressure system will persist a few more days, but another system is unlikely to arrive immediately,” said DHM spokeswoman Bibhuti Pokharel. “Moderate rainfall is expected for a few more days, followed by clearer weather.”

Many are curious about the weather during the upcoming Dashain festival, but officials note that sufficient data for accurate forecasts is not yet available. When asked why rainfall remained average despite initial predictions of reduced precipitation, Madan Sigdel, Associate Professor at Tribhuvan University’s Central Department of Hydrology and Meteorology, explained that Nepal has not experienced the full impact of El Niño. “Although a decrease was anticipated, that did not materialize,” Sigdel stated. He noted that forecasts made in July estimated El Niño’s influence from August to September, but due to the delayed arrival of this influence in South Asia, the expected effects were weaker in August. “The peak impact is projected for November, which is why the monsoon was less affected,” he added. Local seasonal weather systems developing over Nepal’s hilly areas also contributed to higher-than-expected monsoon rainfall. Similarly, in India, some regions with forecasted decreased rainfall exhibited increased precipitation despite El Niño.

The World Meteorological Organization had declared the onset of El Niño in June but confirmed it became fully active by September. El Niño manifests when sea surface temperatures rise in the central Pacific Ocean. According to DHM spokeswoman Bibhuti Pokharel, westerly winds also produced rainfall toward the end of the monsoon. “A low-pressure system appeared near the monsoon’s conclusion, which contributed additional rains,” she explained.

Regarding the winter season, meteorologist Madan Sigdel cautions that El Niño may cause reduced winter precipitation in Nepal. “Its effects have been observed post-monsoon and during winter, as sea surface temperatures have risen by three degrees Celsius,” Sigdel clarified. Citing the World Meteorological Organization, the United Nations Development Programme (UNDP) warns that El Niño will peak toward late 2026, significantly impacting Asia. UNDP highlights possible consequences on agriculture and food security. According to Sigdel, diminished winter rainfall could adversely affect winter crops in Nepal. “Post-monsoon rainfall deficits will influence water resources and crops such as wheat and barley, with impacts likely to persist throughout winter,” he said. Nepal’s average winter rainfall is 66 millimeters, but it has been declining consistently over the past three years. Last year, winter rainfall was about 20 percent below average, according to DHM reports.