Auckland and Northland were hit by more than a thousand bolts of lightning last night and meteorologists are predicting the bad weather will be around for some days.

The foul weather has caused slips and flooding across the North Island and snow has closed some South Island roads.

Deafening claps of thunder shook buildings in central Auckland, where the cavernous nature of some of the streets bordered by towering buildings seemed to amplify the intensity of the noise.

Weather Watch head analyst Philip Duncan said much of the electrical storm involved fork lightning, the most dangerous type.

He said that in such conditions, people should switch off non-essential electronic appliances, such as computers, until the storms have passed.

The stormy conditions are being caused by a low just north of NZ.

Slips and flooding

In the central North Island, continued heavy rain caused slips and flooding resulting in a number of road closures overnight.

State Highway 4 was closed from Wanganui River Road to Raetihi following a major slip.

Traffic was being diverted through SH1, police said.

Shortly after midnight police said SH57 had flooded between Palmerston North and Linton.

Rain also caused slips in the Manawatu Gorge and contractors were called in to keep the road open.

Police this morning warned drivers of high sided vehicles and motorcyclists to avoid SH56 and SH57 near the Manawatu town of Shannon due to high winds.

Icy roads

Motorists in the lower half of the South Island have been warned there is severe ice on the roads.

Police said motorists travelling between Invercargill and Winton should drive with caution as "extreme ice" on the road had made it almost impossible to even stand on.

SH8 was closed between Fairlie and Lake Tekapo due to snow.

Motorists were advised to use chains when travelling on SH73 near Arthurs Pass.

MetService warnings

The MetService this morning said damaging winds for the central and southern North Island were now unlikely, but strong gusts up 100kph in some areas could potentially cause some trouble.

It warned of further heavy rains in eastern areas of the North Island from Coromandel Peninsula to Wairarapa.

Rain will affect most of the North Island but Coromandel Peninsula, the western Bay of Plenty, Gisborne and the Hawkes Bay ranges are likely to bear the heaviest of the falls, it said.

Gisborne's hills and ranges can expect up to 180mm of rain between today and Tuesday night while Hawkes Bay's could see 120mm fall.

MetService's Gerard Barrow advised people in these areas to "look out for rapidly rising rivers and streams, and be prepared for local surface flooding and slips".

He said a deep low moving east over the far north of the country was bringing the rain and wind.

"The low should move gradually away to the east on Tuesday with heavy rain becoming confined to Gisborne," said Mr Barrow.

The east of the North Island can expect heavy rain for the start of the week, although temperatures should rise at the same time.

'Typical July weather

Philip Duncan said there could be some snow on Mt Ruapehu today and possibly tomorrow.

"[But] it should get milder in the north and colder in the south and even out later in the week. We are in for an unsettled month."

A ridge of high pressure over the South Island means the cold weather is unlikely to move out until Wednesday.

Mr Duncan said severe weather was expected next weekend with the country "sandwiched between two lows", and rain and scattered thunderstorms likely.

"It's typical July weather. June was dry and unbelievably cold. The wet stuff's definitely arrived."

- With NZPA