Poor monsoons could dent crop output in India - the world's No. 2 rice and sugar producer, while less rains in soybean areas could make the country, already the world's top importer of cooking oils, more dependent on overseas purchases.
"There is a strong consensus about the possibility of evolution of an El Nino event during the summer monsoon season," said D S Pai, the lead forecaster of the Indian weather office, when releasing the consensus forecast of the South Asian Climate Outlook Forum - a group of global weather experts affiliated to the World Meteorological Organisation (WMO).
Rains could be below average in Sri Lanka, Bhutan, and some parts of Pakistan, while an average monsoon is expected in Bangladesh, Nepal and Afghanistan, Mr Pai said.
A strong El Nino, marked by a warming of the sea surface on the Pacific Ocean, can cause severe drought in Australia, Southeast Asia and India, while drenching other parts of the world such as the US Midwest and Brazil in rains.
But it is a little early to assess the likely strength of El Nino, the WMO weather forum experts said.
"El Nino is still in its neutral phase, not fully established, as it is yet to reach its threshold limit," said Rupa Kumar Kolli, head of the climate applications and service division of the WMO.
A string of global agencies, including the Climate Prediction Centre, have forecast a high chance of El Nino arriving during the Northern Hemisphere summer this year. The WMO assessed earlier this month that an El Nino could develop around the middle of the year.
This forecast followed predictions by other national forecasters, including weather bureaus in the United States, Japan and Australia, that an El Nino event was likely within months.
India suffered a severe drought in 2009 when monsoon rains failed due to El Nino, though in 1997, one of the strongest El Nino years, rainfall was 2 per cent above average.
If rains this year are hit by El Nino, it could force a newly elected Indian government after polls in May to review the policy on grain exports adopted in 2011 on bumper harvests. Good harvests have meant India has allowed exports of rice, wheat, corn and sugar in large quantities.
The June-September monsoon season is vital for India as half of its farmland lacks irrigation. To reduce dependence on rains, the South Asian nation plans to expand its farmland under irrigation by at least a tenth by 2017.
Agriculture accounts for 14 per cent of Asia's third-largest economy, with most Indians living in rural areas. Healthy harvests can help keep a lid on food inflation, which has been stuck at around 9 per cent. India's inflation could remain in the 8 per cent to 10 per cent range if below -average rainfall during the monsoon pushes up food prices, instead of falling to a 7 per cent level by March 2015, Bank of America Merrill Lynch said in a report.
India's weather office rates as normal rainfall between 96 and 104 per cent of a 50-year average of 89 centimetres during the entire four-month season. The last drought with rains below this range was in 2009 and prior to that, in 2004 and 2002.