La Niña is on its way, but will it be enough to help farmers fend off drought this summer?

With farmers in some parts of the country already bracing for drought this summer, La Niña had offered them reason for hope.

But now, according to WeatherWatch, the weather system might be more short-lived than previously thought, and "may not be the silver bullet to fix all the dry issues out there".

Philip Duncan, head forecaster at WeatherWatch, says this La Niña will most likely last around four months - a stark contrast to the one 10 years ago that stuck around for around two years.

"It's a big difference," Duncan told Dominic George on Magic Talk's Rural Today on Tuesday.

"It's a much smaller window to get some of those rainmakers coming in that we need desperately in some areas."

La Niña is expected to peak in December or January, with scientists at Australia's Bureau of Meteorology saying around half their models anticipate a "strong event".

The forecast means the country will have around four months of La Niña conditions, a period with warmer-than-usual sea surface temperatures north of New Zealand and more chance of rainmakers - something farmers are desperate to hear.

"We've got chances of rainmakers coming out of the north, but we've also got high pressures coming out of Aussie getting in the way of those - so it's just not quite as clean cut as saying it's the strongest in 10 years," Duncan said.

"If we were just two flat islands it would be much easier to say La Niña is cloudier, more humid and a higher chance of rain. But our mountains and ranges completely throw that."

Duncan said it was hard to pinpoint exactly what an El Niño or La Niña event would bring in New Zealand as there were so many variables.

"It never puts its thumbprints there in the exact same spot. It's always a little bit different, that's because airflows are never the same and our mountains and ranges then break it up. 

"But to make it really simple, La Niña increases nor'easters. Nor'easters come down across the country [and] if you know what a nor'easter is where you live locally you can then work out, does that mean I'm on the dry side or the wet side? 

"If you're in Southland and Otago - apart from coastal Otago, that is - there's a good chance you're in for a warmer, drier summer. The same with Kapiti Coast, they can end up with a hotter, drier summer as well - those nor'easters come over the hills and they're putting the moisture up around Hawke's Bay and Gisborne."

Last year brought crippling drought for many parts of the country, in what was an extremely tough time for farmers. Now, with more dry weather possibly on the horizon, they are already making preparations for another tough summer.

And though La Niña may be short-lived, farmers will be hoping it brings crucial rain to the places where it's needed most.