The current El Nino phenomenon, which has spawned drought across much of the Asia-Pacific, wildfires in Australia and powerful storms in the United States, is perhaps the strongest ever measured and is peaking this month, experts say - and global warming may be exacerbating its effect.
"It is one of the top three El Ninos of the last 100 years," Bangkok-based Mr Sanny Jegillos, senior adviser for crisis prevention and recovery at the United Nations Development Programme, told The Straits Times.
Mr Jerome Lecou, a climate expert at French weather service Meteo France, went further. "It is probably the most powerful in the last 100 years," he told news agency Agence France-Presse.
Accurate measurements have existed only since the mid-20th century. The previous strongest El Nino recorded was in 1997-98. Back then, the phenomenon raised air and sea temperatures, killing an estimated 16 per cent of marine coral reefs. It also triggered record rain in California and severe drought in Indonesia. Tens of thousands died in related events.
This time, the cyclical phenomenon is even stronger and has so far wreaked havoc mostly around the Pacific Rim and parts of south Asia.
"It has peaked and we will see adverse impacts in the next few days," Mr Jegillos said. Heavy rain has, in recent days, triggered floods and mudslides in Paraguay, Uruguay and Argentina, leaving over 150,000 homeless.
In the central and south-western US, severe weather including tornadoes has claimed at least 43 lives this month.
This winter, California, Arizona and New Mexico will get more than their normal share of winter storms,Professor Dave Gutzler, a climatologist at the University of New Mexico, predicted this week.
The recent flood disaster in Chennai, on south India's east coast, when much of the city including its international airport was under water in the first week of this month, was also attributed to El Nino.
Meteorologist Sivananda Pai and his colleagues at the India Meteorological Department in Pune, India, had issued their first warning as early as October, when they worked out that the seasonal storms forming in the Bay of Bengal were not going to move north as usual, but due west instead under the influence of El Nino - a belt of warm air and ocean.
The storms normally pick up energy on their way north, and hit the coast of eastern India, Bangladesh or Myanmar as full-blown cyclones, Mr Pai said by phone. But because they did not traverse so much open sea on their westward path, they did not pick up speed. Instead, when reaching land, they dumped torrential rain, inundating Chennai for days.
"When the temperature of the air increases, the moisture-holding capacity of the air increases; then there will be more rain," said Mr Pai. "That is why people are also talking about climate change."
"The combination of record warmth one year followed by an El Nino the next is unique and the climatic implications are uncertain," aid agency Oxfam said in October. "If 2016 follows a similar pattern, we are entering uncharted waters."
In the Australian state of Victoria, where more than 100 homes were razed in a Christmas Day bush fire, the authorities have warned that some blazes would continue to burn as temperatures were set to soar again as high as 38 deg C in the lead-up to the new year.
Mr Jegillos sounded a warning, especially about Papua New Guinea. "For Papua New Guinea, many of its farmers are subsistence farmers and there is food insecurity anyway, and El Nino has been severe on their crops.
"Even if the next monsoon season in October-December is normal, the impact on agriculture, the eco-system and water resources has been severe enough for them to face problems until 2017."