Unstable weather conditions have seen parts of New Zealand zapped by 1794 lighting strikes over the last 24 hours.

One bout saw northern Auckland struck by lightning seven times in 10 minutes, between 5.35pm and 5.45pm today.

MetService forecaster Allister Gorman said it was all down to cold conditions in the upper atmosphere.

"Western areas of the country have been experiencing thunderstorms these last couple of days, due to very unstable conditions over the country at the moment.

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"Early this morning there were some [strikes] over the sea either side of Auckland, and this evening with this band it's slightly more intense, so some thunderstorm activity has come over the North Shore area."

Gorman said they also had reports of hail over Auckland.

"We have some very cold temperatures in the upper atmosphere that came over New Zealand a couple of days ago.

"That's been with us since Thursday and is likely to stay with us another day or two.

"Those colder temperatures in the upper atmosphere make things unstable, where the heat from the sea can cause these clouds to build up to thunderstorm clouds a lot easier."

There's a moderate risk of further thunderstorms overnight for the western side of the North Island.

For Auckland the thunderstorm risk continues until Sunday evening.