Most of the country is in for unsettled, cooler weather on Christmas Day as a wet front makes its way up the country.

It was hot, sunny and humid - and for some thunderstorms came almost out of nowhere in the day of extremes that hit the upper North Island yesterday.

The summer-like weather is set to fade this week with rain forecast for much of the upper North Island from tomorrow.

The weekend will be at least partly wet for most of the country, forecasters said this morning.

Parts of the North Island are being warned to brace for possible slips and surface flooding as a low brings rain to much of the country today.

Boulders weighing up to 200 tonnes have blocked access to Milford Sound as galeforce winds and driving rain sweep across the country.

Infestations of flies are plaguing householders as temperatures start to climb. Mid-20C...