Tauranga is on track for a cold snap next week, with the potential for wind gusts of up to 100km/h, after an unusually warm start to autumn.

According to the latest Niwa regional predictions, May promises to be a month of two halves, and one local retailer told the Bay of Plenty Times Weekend winter coats were already flying out the door.

Niwa principal scientist Chris Brandolino said regional predictions for May to July indicate temperatures were most likely to be above normal in Tauranga and the Western Bay.

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There was a 50 per cent chance rainfall would be above average for this time of the year.

Mr Brandolino said temperatures on Tuesday were likely to be in the high teens or early 20s. Wednesday was expected to be a lot cooler; in the mid teens, with the potential for wind gusts of 70-80km/h and possibly up to 100km/h, he said.

Mr Brandolino said it was too early to predict how long the cold snap would last, and the real litmus test would come after next week's cooler spell, but Tauranga's weather was expected to return to more balmy temperatures later next week.

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Throughout the country, mean temperatures for May were in general two degrees above average.

Mr Brandolino said some of the factors coming into play were unusually warm sea temperatures surrounding the country, and a huge high sitting over New Zealand and to the east of the country, which had spared many areas from colder weather.

Despite the change, Niwa predicted that temperatures between May and July were "very likely" to be above average in all regions of the country.