US meteorologists say an El Nino has formed in a warmed-up Pacific Ocean and is expected to grow strongly.

The US Climate Prediction Center said the El Nino conditions had developed over the past month and were expected to strengthen into the northern hemisphere winter ‌of 2026-27.

El Nino ‌is a phenomenon that occurs naturally, when weakening trade winds cause warmer ocean waters to build up in the central and eastern equatorial Pacific.

This typically leads to higher global temperatures and altered weather patterns, bringing the risk of drought to some regions – such as Australia – ‌and heavy rainfall ‌to others.

“El ⁠Nino is likely to have a negative impact ​on crop yields in South-East Asia and India, where El Nino is typically associated with below-normal rainfall,” said Kyle Tapley, enterprise sales executive at Vaisala Xweather’s WeatherDesk.

The monsoon delivers nearly 70 per cent of India’s rainfall and is vital for the agricultural ⁠sector, which accounts for about 18 per cent of ‌the ​nearly $US4 trillion ($A5.7 trillion) economy.

Below-normal rainfall could mean smaller harvests of crops such as ​rice, cotton ‌and soybeans, while also weighing on winter crops.

Meanwhile, Indonesian rice farmers are ​racing to get ahead of the usual planting schedule as they battle the threat of a lengthy dry spell this year.

Malaysia’s economic ​minister ​warned that El Nino could ​cause crop yields to fall by an ‌average of between 8 per cent and 10 per cent this year.

While the conditions can increase the danger of bushfires in Australia, Tapley said El Nino typically leads to a less-active hurricane season in the US.

“We expect a below-normal Atlantic hurricane season this year. However, it is important to remember that a strong hurricane is still ​possible even in a less-active hurricane season.”

The US hurricane ​season began on June ⁠1 and runs through November 30.