Weather: Don't be fooled by the morning's dry conditions

A soggy weekend is in store across the country.

The heaviest rain and snow is coming to eastern parts of the South Island, with a warning and watches issued.

MetService says a "complex low pressure system, with a number of associated fronts, is forecast to move onto New Zealand from the Tasman Sea this weekend".

Meteorologist Angus Hines says 30 to 50 centimetres is forecast for the higher Arthur's Pass.

"That is certainly a decent amount of snow. If that falls on the road up there, that's going to have a signficant effect on travel."

There's a heavy snow warning for parts of Canterbury and Otago, falling to 300 metres.

Hines says there could be significant impacts on travel throughout the weekend. 

"We're forecasting 30, even 50cm of snow on the higher passes up there, on Arthur's Pass, as well as other higher roads around the South Island," he told Newshub.

And don't be fooled by the early morning conditions.

"It may be dry when some people wake up, but it won't take long until that rain really starts to set in for those areas, and the snow for those higher areas. Expect periods of wet weather, periods of rain and snow right through the day on Saturday and into Sunday morning."

WeatherWatch said the upper half of the North Island will have "sunny spells and a few showers, more so from midday", but there's a "risk of thunder for south Auckland, Waikato and Bay Of Plenty then easing later on".

The forecaster is predicting a relatively warm high of 18C up north, but a chilly 2C is possible in Southland and Otago.