US officials narrowed the odds on an El Nino kicking in as some private meteorologists said that the impact of the weather event may already be being felt, including in heavy US rains.
The Climate Prediction Center, part of the Maryland-based National Weather Service, raised to 70%, from 65%, its estimate of the likelihood of an El Nino starting during the northern hemisphere summer.
The chances are 80% of the weather pattern - linked to warmer Pacific water temperatures, and a range of climatic effects from Australia to Brazil – having started by the autumn or winter.
"Above-average sea surface temperatures expanded over the equatorial Pacific Ocean during May," the Climate Prediction Center said, adding that "all of the Niño indices increased during the month".
Assuming the El Niño forms, "forecasters… slightly favour a moderate-strength event during the Northern Hemisphere fall or winter", the centre added, if noting "significant uncertainty" over this forecast.
The forecast puts the CPC in line with Australia's Bureau of Meteorology, which on Tuesday restated the chance of an El Nino as being at least 70%.
Official meteorologists in the likes of Colombia, India and Japan have also cautioned over the chance of the weather pattern returning this year.
Some private forecasters believe there are signs that the impact of the weather pattern may already be being felt, with Gail Martell at Martell Crop Projections saying that storms in the US this week "may be linked to a growing El Niño influence".
Some central Plains and western Corn Belt crops have sustained damage from hail storms this week, although the precipitation has brought relief to drought hit areas of the Plains.
"Sudden heavy rainfall in Texas and Oklahoma" in late May, of 4-5 inches, "was a symptom of a growing El Niño influence," Ms Martell said, noting that Plains weather is sensitive to the weather pattern, typically becoming wetter.
"The Midwest also is influence by the El Niño receiving heavy rain, though east of the Mississippi River, summer growing conditions often become very dry."
At weather service WxRisk.com, David Tolleris, noting that weather models show "very wet and very cool" conditions for the second half of June, said that "this is typical for an El Nino in the early summer".
While the summer typically bring concerns over hot weather, which can set back corn pollination, this time "the issue may end up being growing degree days", in essence a measure of the natural energy that plants receive, Mr Tolleris said, "if, if this wet, cool pattern holds into August-September".
Indeed, the prospect of an El Nino, and its timing, are of great interest to agricultural commodity investors, given the potential impact on yields.
For instance, the southern Plains rains, while in time to help cotton seedlings, are viewed as largely too late to boost prospects for the hard red winter wheat crop grown in the region.
Separately, Informa Economics on Thursday cut its forecast for this year's US winter wheat harvest by 100m bushels to 1.396bn bushels , including a forecast of 744m bushels for the hard red winter wheat crop.
However, cooler Midwest temperatures are viewed as a boost to prospects for US corn, with its later growing season, with research by Societe Generale, for instance, noting that "corn yields are usually improved in an El Nino".
Also in the US, soybean harvest prospects are typically improved by an El Nino, "with cooler and damper conditions supporting yields", the bank said.
Meanwhile, the weather pattern's role in bringing dryness to some parts of Brazil can, initially, pressure prices too, in improving transport and helping to "keep the global trade pipeline supplied".
"However, continued warm, dry weather in Brazil in December-February can have adverse effects on the following crop," prompting upward pressure on soybean values.
Elsewhere, in the oilseeds complex, palm oil prices are often supported by El Ninos, "particularly strong events", which "bring dry weather to the Pacific Rim, threatening palm oil crop conditions in countries such as Indonesia and Malaysia", SocGen said.
Indeed, Standard Chartered has recommended an investment of going short Chicago's January 2015 soyoil contract, while going long on January palm oil, based on the idea that the weather pattern tends to support soybean production, but undermine palm output.
However, StanChart did voice concerns about the potential hit to India's soybean harvest from an El Nino, which often weakens the monsoon, noting that the 2009 event "slashed yields by around 10%" thanks to dryness.
The weather pattern is also "bad news for Australia's wheat yields", the bank said, noting that southern and eastern areas of the country "are particularly vulnerable to El Nino conditions", typically manifested in undue dryness.
Meanwhile in sugar, "Brazil's cane yields could be dealt a double blow by an El Niño event, similar to 2010, due to low rainfall at the start of the cultivation period and excessive precipitation during the harvest period," StanChart analyst Abah Ofon said.
With the El Nino typically causing dryness in Thailand, the second ranked exporting country, the bank has forecast a small world production shortfall in 2014-15.