Dry, cold rest of October in store as we wait to see if El Niño arrives or fizzles

As we charge towards summer, don't expect sustained warm weather just yet.

"October's going to be on the cool side for much of the country," NIWA principal forecasting scientist Chris Brandolino told TVNZ1's Breakfast today. "So no sneak peeks of summer, it looks like - at least very limited."

And as we teeter on the edge of a possible El Niño, there's some discouraging news for farmers: October is looking to be quite dry as well.

"We've already started out pretty dry across much of the upper South Island, and that doesn't bode well because some people have actually started irrigating," Mr Brandolino said. "That's pretty unusual given that we're coming out of winter.

"The fact that we are starting off dry in some areas, and the fact that we're looking at dryness in the month of October - that could basically continue on."

Mr Brandolino emphasised that El Niño hasn't developed yet, and it may not this year. If it does develop, it's looking like it could be a weaker system than in years past, he said. We'll know for sure sometime between now and the end of the year, he predicted.

"Generally speaking, you can conjure up images of more rain than usual across the western part of both islands, and less rain than usual across the eastern part of both islands," he said of El Niño years. "That's not always the case. We know the average outcome of El Niño, but no El Niño is average."

Mr Brandolino compared El Niño to a hand on a steering wheel. Historically, that grip has been about 25 per cent.

"But because this El Niño, should it come to fruition, is expected to be on the weak may not have that firm grip on the steering wheel," he said. "It may allow for other people to take the steering wheel.

"So there may be these episodes when the wind comes from the west, which is typical of El Niño, and then that stops. We get other influences, say from the north and northeast."

Those in the agricultural sector who rely on steady rainfall will be keenly watching along with NIWA staff to monitor the evolution of the potential weather influencer, he said.

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We won’t get much of a sneak peek of summer just yet, NIWA principal forecasting scientist Chris Brandolino predicts. Source: Breakfast