When will the big chill end?

Snow in Gisborne. Photo / Katie Dyer (via Facebook)

The cold snap lingering throughout the country this month has broken records - but it's not here to stay.

Rain is forecast to start tomorrow night for most of the North and South Island, with a northerly flow bringing warmer temperatures.

The high that has been over the country for the past week, bringing clear blue skies during the day but frosts and freezing temperatures, has moved away.

Niwa data shows seven of the 30 weather stations from Cape Reinga to Stewart Island had the lowest maximum temperatures on record for July, with Ohakune barely reaching 2.2C on July 9.

Five towns - Kaitaia, Kerikeri, Warkworth, Te Kuiti and Greymouth - clocked their lowest temperatures in July since records began.

But MetService meteorologist John Law said that would change.

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Rain and winds sweeping the country from tomorrow night with a northerly flow would become heavy in the north and west tomorrow, Mr Law said.

WeatherWatch head analyst Philip Duncan said the front coming in from the Tasman Sea would move across the country throughout Wednesday.

The weather should clear on Thursday and Friday.

Rain would set in again on Saturday and there was a possibility of isolated snow showers on Sunday, Mr Duncan said.

"There may be a few frosts in the morning for a few sheltered parts of the country but generally speaking the frosts are out of the window now for a few days.

"Temperatures look like they should be slightly above average [on Friday] so it should be a nice end to the week. But Saturday is seeing a large low start to move in so there'll be areas of heavy rain and there could be some gusty winds."

More than 6000 people have hit the slopes at Turoa and Whakapapa every day since Saturday.

Mt Ruapehu executive manager Simon Dickson said the large crowds were turning up to ski, board, sled or simply play in the snow and number weren't expected to slow down.

Niwa climate scientist Gregor Macara said the record cold weather during the week was caused by a cold southerly flow, followed by a high-pressure system bringing clear skies and little wind to most of the country.

Weather forecast

Auckland: Showers begin tomorrow afternoon and rain sets in on Wednesday, then ease on Thursday. Temperatures around 15C.
Hamilton: Cloud tomorrow, rain on Wednesday easing to showers on Thursday. Temperatures around 14C.
Wellington: Mostly fine tomorrow, rain developing on Wednesday and Thursday. Temperatures around 13C.
Christchurch: Morning frost tomorrow, cloudy periods on Wednesday and showers on Thursday. Temperatures around 13C.
Dunedin: Cloud increasing tomorrow and Wednesday with showers on Thursday. Temperatures around 12C.