HONG KONG—The weather phenomenon El Niño could be one of the worst in the last 65 years, and a number of agricultural commodities are starting to feel the heat.

Ocean and atmosphere indicators that measure the strength of weather phenomenon El Niño are now comparable with the significant events of 1997-1998 and 1982-1983, Australia’s Bureau of Meteorology said Tuesday. Japan’s Metrological Agency said ocean temperatures last month were the highest for an October since 1950.

El Niño occurs when winds in the equatorial Pacific slow down or reverse direction. That warms water over a vast area, which in turn can upend weather around the world. The severity of the phenomenon is measured by ocean temperatures and atmospheric convection activities. The phenomenon typically reduces rainfall across parts of southeast and southern Asia as it brings precipitation to the western U.S. and parts of South America.

El Niño events can lead to severe drought in parts of Southeast Asia and heavy flooding in North America, all of which causes challenges for farmers.

In October, there were warmer-than-normal conditions in India and the northwestern part of South America. There were cooler-than-normal conditions in the southern part of South America and drier-than-normal conditions in Indonesia and from Australia to the western part of the South Pacific, the Japanese weather agency said.

A number of agricultural prices have rallied off their lows on fears of weather-related supply shortages. Sugar prices have risen 33% over the past three months; dairy is up 56% while palm oil has gained 13.3% over the same period.

In India, the lower than normal monsoon rains have put significant pressure on the prices of vegetables and pulses in the country. Prices for chana, also known as chickpeas, have risen nearly 20% since mid-September on supply concerns and India’s National Commodity and Derivatives Exchange has now introduced a special margin on its November, December and January contracts in a bid to temper volatility.

The El Niño event is expected to peak before the end of the year before gradually easing in the first quarter of 2016, according to the two weather services.