A combination of heavy rain, a king tide and severe gales whipping up big waves could cause damage in the Western Bay this weekend.

This afternoon the Metservice most of the upper North Island under a severe weather watch for Sunday.

Metservice meteorologist April Clark said a watch would not normally be issued more than 48 hours in advance, but the incoming low could cause significant disruptions so people needed to be on alert.

"It is pre-emptive since there is the potential for quite severe impacts, including disruptions and possibly damage."

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The watch was likely to be upgraded to a warning, she said, but the expected path of the low bringing the weather was not yet clear.

The most recent weather models showed the centre of the low tracking south across the upper North Island on Sunday.

Clark said that if it tracked more north or west its impact could be less severe, but if it moved further south the Western Bay would be in for even stronger winds.

The low was expected to bring severe gale easterlies until 6pm and heavy rain - possibly 70mm over 12 hours or less - over the course of the day, with the wet weather expected to continue on Monday.

Big waves could inundate exposed eastern coastlines, especially in combination with Sunday's king tides, which will be at their highest around 8.30am and 9pm.

A Tauranga City Council spokeswoman said council staff were monitoring the weather closely but had not made any specific preparations as it was only a watch.

Winter Nights Winter Lights, launching tonight, was expected to go ahead as planned on all four nights. Any weather-related cancellation decisions would be made on the day.

"Until then, we encourage people to dress accordingly, wrap up warm, brave the rain and enjoy the lights."