MetService says Kaikoura and North Canterbury could be in for some heavy rain overnight as the stormy weather that's buffeted parts of the North Island on Sunday moves south.
Heavy rain and gales have knocked out power to about 1000 homes in Wellington on Sunday night, and slowed traffic to a crawl around the North Island.
Wellington Electricity says about 1000 customers lost power just before 7pm in Karori, the Miramar Peninsula and Wainuiomata.
The company says power to most households has been restored and crews were patrolling the lines, clearing tree branches and looking for faults on Sunday evening.
Earlier on Sunday the police asked motorists to be patient as traffic on roads already busy with homeward bound holiday makers, slowed to a crawl north of Auckland and also on the Desert Road due to the heavy rain and gales.
MetService Severe Weather Forecaster Andy Downs says the rain band responsible for the heaviest falls is now leaving the North Island, but could bring downpours to Kaikoura and North Canterbury overnight.
He says by dawn the rain there should start to abate, but even when the stormy weather subsides it's still likely to be unsettled and showery.
Mr Downs says warm humid conditions on Monday could trigger thunderstorms in the lower North Island.