Those in the upper North Island might want to avoid outdoor activities for the next day or two, with heavy rain to start the week.

A low over the north Tasman Sea would move onto the North Island Sunday night, bringing heavy rain on Monday from Auckland, across through Coromandel and Western Bay of Plenty for Monday, with several weather watches in place.

That low would become slow-moving as it crossed over the island late Monday and on Tuesday, bringing periods of heavy rain with isolated thunderstorms to the northern parts of the North Island.

The heaviest falls were expected about Coromandel Peninsula and Bay of Plenty west of Te Puke from Monday afternoon to Tuesday evening, and a heavy rain watch was in force for these regions.

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It comes after a widespread burst of thunderstorms tracked across Northland and Auckland early Sunday morning - and more than 1300 lightning flashes were detected within an hour.

On Monday Auckland's forecast included periods of rain, heavy and thundery at times, with northerlies and a high of 16C.

MetService forecaster Paul Ngamanu said the South Island and lower North Island were in for a mostly fine day Monday, with just some cloud and a few showers.

The slow moving front should continue to affect the North Island on Tuesday, with rain expected for many areas.

On Wednesday, the front over the North Island should move away to the northeast, and a narrow ridge would spread fine weather over the country.

Another front would then move on to the southwest of the South Island Thursday night, and continue northeast on to the North Island later Friday while weakening.

The front would be preceded by a strong northwest flow, and followed by disturbed westerlies.