The last remnants of former tropical cyclone Evan could make it a sodden Christmas in the North Island, but South Islanders will be savouring Christmas lunch in the sun.

Although the deep low pressure system that remains from Evan has made forecasts less predictable, both and the Metservice agree the deep south will have the pick of the bunch.

Metservice is predicting rain with warm north-easterlies in Northland, Auckland, Waikato, the Bay of Plenty as well as Taranaki across to Hawke's Bay. forecasters are more optimistic, predicting rain and showers clearing from the morning in these areas, but with the humidity levels remaining high.

Weatherwatch forecaster Phillip Duncan said the remnants of Evan will lie west of the North Island and the tropical air that come with it will make it seem warmer than the actual temperatures - around the "mid-20's" - across the North Island.

"The 'feels-like' temperature will be in the low to mid-30's in these regions, especially if the sun comes out for a bit as well," said Mr Duncan.

The capital looks set to have a mostly fine day, with highs in the mid-20's, with morning showers clearing before the Christmas ham is carved.

Both weather forecasters predict the South Island to be the place to be, with the entire island set to celebrating in the sun, with highs of 30 degrees and above in central Otago and inland Canterbury, with clear skies and light winds.

Metservice weather forecaster Brooke Lockhart said former tropical cyclone Evan had injected more uncertainty than usual in their predictions, although it was continuing to weaken as it approached New Zealand.