Farmers beware: a build-up of warm water in the tropical eastern Pacific has lifted the odds for an El Nino forming late this spring, the Bureau of Meteorology said.

Five of the eight models used by the bureau now point to El Nino thresholds being crossed, a shift in climate patterns that would typically produce lower-than-average rain across eastern Australia.

An El Nino can point to a dry spell for eastern Australia - which would be bad news for dairy farmers such as Brendan Hayden, from Pilton, Queensland, who are already being forced to provide fodder for their herds. Credit:Peter Rickards

"The ocean is primed for an El Nino but it will need a push from the atmosphere" to get there, Robyn Duell, a senior climatologist at the bureau, said. "It will depend a lot on what happens to the trade winds in the next couple of weeks."

At present, the odds for an El Nino are about 50-50 but even a near miss can still translate into lower-than-average rain and hotter temperatures for much of the country. Given the winter outlook is already pointing to the continuation of the drier-than-usual conditions, those areas already in drought might be in for an extended dry spell.