The El Nino effect with its westerly winds is predicted to continue and weaken in Whanganui through this summer, forecasters say.

The National Institute of Water and Atmospheric Research (Niwa) is predicting average or higher temperatures for the next three months, and average or lower rainfall for the wider Whanganui region.

This summer's El Nino effect is a strong one, linked to higher than usual ocean temperatures. Those temperatures are now reducing, but are still 2degC higher than usual.

The last three El Ninos happened in the 1972-3, 1982-3 and 1997-8 seasons, and all made for extremely dry seasons in parts of New Zealand. Strong westerly winds are typical of them, along with drier-than-normal conditions in the north and east.

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This spring's westerly winds are likely to last into autumn, Niwa's latest report says. By the July-September quarter the climate should be back to either a normal pattern or a La Nina pattern - with calmer days and more wind and weather coming from the north.

The risk of an ex-tropical cyclone passing close to New Zealand is slightly higher than usual this year and Cyclone Ula may bring rain to northern New Zealand tomorrow.

Typically, such cyclones bring heavy rain and strong winds.