Temperatures are set to plummet by as much as 10 degrees Celsius this Queen's Birthday weekend as a snowy blast hits New Zealand.

Forecaster WeatherWatch is warning Kiwis to enjoy the next two days of warmer than average weather because "it's about to change".

The coming late autumn storm will produce rain and heavy snow with the worst of the weather to hit on Saturday.

Auckland's forecast high could drop from 20C today to 13C on Saturday, while Hamilton will plunge to a daytime high of 12C.

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The Bay of Islands will drop from a high of 22C tomorrow to 14C on Saturday.

"Hawke's Bay, arguably one of the more sheltered, sunnier and warmer regions ... will go from highs in the early 20Cs this week to a windy southerly on Saturday and weekend highs of only around 12," WeatherWatch said.

In the South Island, Christchurch will fall from a high of 19C today to only 9C on Saturday with WeatherWatch warning "it gets colder the further south you go".

This will lead to Queenstown dropping from a high of 14C today to highs on Saturday and Monday of 5C with snow showers.

Dunedin temperatures will fall by 11C from a high of 16C today to only 7C on Saturday with snow down to 400m and hail to sea level.

However, our mountains and ranges mean not everyone is in for "bad" weather, with sunny dry and mild weather still forecast for several regions this long weekend.

After a week of rain the West Coast is the place to be this Saturday as early cloud and showers clear to a dry and sunny afternoon. Conditions are mostly dry in Gisborne too, until the very end of the day when southerlies arrives.

The West Coast is again the place to be on Sunday with clear sunny skies and dry, even with the cold southerly. This dry weather spreads east into Canterbury as the day goes on too.

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In the North Island it's eastern Coromandel Peninsula, Bay of Plenty, parts of Waikato and after morning cloud or showers clear both Hawke's Bay and Gisborne look pretty good - but colder.

Monday kicks off with warmer westerlies in a number of regions, so those in the east are most likely to have the best weather with sunnier, drier conditions and a temperature bump of a few more degrees.

It's possible northern areas like Northland, Auckland and Waikato may also have a fairly good Monday too, but there is some risk of a few showers, especially later.

The forecast beyond this weekend's freeze is uncertain.

A warmer high could blow in from Australia, but WeatherWatch was having increasing confidence that another deep Southern Ocean low would instead come in with more cold temperatures.

"Talk about a weather pattern shift!"

Queens Birthday traffic:

Commuting around Auckland might be disrupted over Queen's Birthday weekend due to construction work connected to the City Rail Link project.

The areas impacted most are part of Mount Eden and some rail services on sections of the Southern and Eastern Lines.

Buses will replace trains on some sections of the Southern and Eastern Lines due to upgrades, including the construction of an additional line for a third platform at Otahuhu Station, of the Auckland rail network.

Meanwhile, no weekend construction is planned for CRL's Lower Queen St/Britomart and Albert St sites in central Auckland.