MELBOURNE, Australia — An El Nino weather pattern, which can parch Australia and parts of Asia while bringing rains to South America, will probably develop by July, according to forecaster MDA Weather Services.

The chances of El Nino emerging later in the northern hemisphere summer are 75 percent, said Donald Keeney, senior agricultural meteorologist at Gaithersburg, Md.-based MDA.

El Ninos affect weather worldwide and can roil agricultural markets as farmers contend with drought or too much rain. The phenomenon often touches off warmer winters across the northern U.S., heavier rains from southern Brazil to Argentina and drier conditions across southeast Asia, Indonesia and eastern Australia. It also can lead to a calmer Atlantic hurricane season and a stormier winter in the U.S. South.

“There is a high probability of El Nino developing later this summer,” Keeney said by e-mail in response to questions. “This should become most pronounced in mid to late summer.”

The U.S. Climate Prediction Center issued an El Nino watch this month. There’s a 52 percent chance that the Pacific Ocean will warm enough to trigger the weather pattern late this summer or in early fall, according to climate scientist Michelle L’Heureux. There’s a 75 percent chance that one will occur in late 2014, according to a report in the journal PNAS last month.

Australia’s Bureau of Meteorology said March 11 that most climate models show temperatures approaching or exceeding El Nino thresholds during the austral winter.

Australia’s winter begins in June. The pattern is associated with below-normal rain in the second half of the year across large parts of southern and inland eastern Australia, according to the bureau.

A record 79 percent of Australia’s Queensland state is in drought, threatening cotton and sugar production and boosting cattle slaughter. Rubber output in Thailand, Indonesia and Malaysia is set to drop 6 percent to 8 percent this year because of dry conditions, according to the International Rubber Consortium Ltd. Dry weather parched oil-palm trees in Indonesia and Malaysia this year.

El Nino typically creates very ideal growing conditions in the U.S. Midwest during the summer, said Art Douglas, meteorologist at Creighton University in Omaha, Neb.

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