World farming was put on alert for potential weather upsets, likely ranging from South American floods to South East Asian droughts, as official forecasters declared the first El Nino in five years.
The Japan Meteorological Agency said that an El Nino weather pattern had emerged in the spring, and was likely to continue into the autumn.
The statement came minutes before the Australian Bureau of Meteorology, which had previously warned that the chances of the weather pattern emerging were triple the typical rate, said that "the tropical Pacific is in the early stages of El Niño".
A key tracker of the phenomenon had been "raised to El Nino status".
Key indicators on the weather phenomenon, which is linked to warmer-than-usual Pacific water temperatures, "have shown a steady trend towards El Niño levels since the start of the year," the Australian Bureau of Meteorology said.
"International climate models surveyed by the bureau indicate that tropical Pacific Ocean temperatures are likely to remain above El Niño thresholds through the coming southern [hemisphere] winter and at least into spring."
The world was put on alert for an El Nino last year, and while it was never deemed to have full developed, some mild versions of weather patterns typical of the event emerged, with dryness for instance in South East Asia early in 2015, which has caused some downturn in palm oil production.
However, a fully-fledged El Nino would be likely to cause more significant effects, with the Australian Bureau of Meteorology noting that, for example, the even " is often associated with below-average winter and spring rainfall over eastern Australia, and above-average daytime temperatures over the southern half of the country".
The bureau's statement comes only the day after Australian fertilizer-to-explosives group Incitec Pivot cautioned that thanks to dryness "Australian growing conditions at the moment look quite challenging for the winter crop", which is currently being planted.
Other weather conditions typically associated with El Ninos include dryness in parts of eastern South America, and potentially damaging dryness for instance for Colombian coffee plantations, and a lack of rain too in West Africa, the main cocoa-producing region.
Conversely, parts of southern Brazil can receive excessive rainfall, potentially hampering cane harvesting and lowering sugar concentrations in crop – albeit boosting agricultural yields.
In the US, El Nino is associated with cool and wet weather in many major growing areas which could resolve drought in southern states and boost Midwest corn yields - albeit potentially impairing the quality of crops such as wheat.
Indeed, "heavy, recurring showers in the Great Plains and Midwest may be consequence of a strengthening El Nino," said Gail Martell at Martell Crop Projections.
"This climate anomaly is a heavy rainmaker for the central US."
Other weather factors linked to El Ninos include weak Indian monsoons. Official Indian meteorologists have already forecast a slightly below-average monsoon this year, with rains at 93% of the typical rate.
Indeed, research by Societe Generale has revealed cotton, of which India is the top producer, as a commodity which has witnessed "significant price spikes during El Nino periods", with cocoa and soybeans too.
Indeed, top-performing US-traded agricultural commodity during El Ninos is typically soyoil, according to the bank, as South East Asian dryness saps output of rival vegetable oil palm oil.
Soyoil is "highly correlated to palm oil that can be impacted by drought in Indonesia and Malaysia", SocGen said in a report last year.
However, the ability to make accurate predictions of El Nino impacts is hampered by the range of other effects also influencing weather patterns.
In Australia, the Bureau of Meteorology said that while El Ninos typically bring eastern dryness, "the current May to July outlook suggests much of Australia is likely to be wetter than average.
"This is because a warmer-than-average Indian Ocean is dominating this outlook."
It is not until the second half of 2015 that El Nino "is expected to become the dominant influence on Australian climate".
In the last El Nino, in 2009-10, while weather in the May-to-October period conformed to the typical pattern, proving "rather dry over much of the country", November, "paradoxically… ushered in a wet period over the eastern half of the country".
By Mike Verdin