A fine and mild Queen's Birthday weekend is ahead for the North Island, but forecasters say it's the calm before another southerly storm sweeps across the country early next week.

And while the north will enjoy temperatures in the high teens, the South Island is bracing itself for a wet long weekend.

Fronts are already building up from the south, said MetService forecaster John Law.

Heavy rainfall with severe weather warnings are expected for the western side of the Southern Alps, as well as the Otago and Canterbury high country areas.


Tomorrow's temperatures will be mild, however, with Auckland expected to reach 18C, and 17C forecast for Napier, Palmerston North, Wellington, and Christchurch. Dunedin can expect 14C.

The best of the weather will be on the North Island's east coast, forecasters expect.

"As we go through the long weekend, it's a case of having high pressure over the northern parts of the country, which is going to be good news for most of the North Island," Mr Law said.

"We'll find a westerly breeze, bringing perhaps more cloud in western places of the North Island but the eastern side looks fine and dry. The South Island is a wetter story."

By the end of Queen's Birthday Monday, the rain might be pushing towards the more central parts of the country - Nelson, Wellington, Wairarapa, and Taranaki.

And by next Tuesday, another cold southerly - similar to the polar blast which iced the country earlier this week - will return, Mr Law said.

Canterbury Highway Patrol urged motorists to drive carefully this weekend, with long trips, cold conditions and alcohol adding to the risks on the roads.

"Motorists need make sure they're driving to the conditions and increasing following distances, particularly if they strike wet weather and poor visibility," says Senior Sergeant Phil Newton.


"Holiday weekends often mean heavy volumes of traffic on the roads. Motorists should allow extra time for their journeys, and be patient and courteous with other road users."

Events such as the Otago Motorcycle Club Brass Monkey Rally in Central Otago are expected to generate significant additional traffic on the roads.

Police will be enforcing a reduced speed tolerance of 4km/h this weekend. The Queen's Birthday weekend period officially starts at 4pm today and ends at 6am on Tuesday.