Motorists are being warned of possible closures on Auckland's motorway near the Harbour Bridge as a king tide is expected to coincide with wet weather this weekend.

The NZ Transport Agency said the combination of the high tide and heavy rain could cause low-lying sections of the motoway to flood on Sunday evening.

The closures were likely to affect a section of the motorway on SH1 from the Esmonde Rd Interchange to Onewa Rd Interchange, headed south.

MetService shift forecaster Larissa Marintchenko said Auckland and Northland was expecting an onslaught of bad weather over the weekend.

The worst of which would fall on Sunday night, which a low pressure system would likely create a strong northeasterly wind and rain.

It's a weekend of two halves. Here's a look ahead to the weekend weather. https://t.co/aotHEz7FMr https://t.co/HupFYQKjRA ^JL

— MetService (@MetService) July 13, 2018

"King tides are also expected in Auckland and Northland on Sunday night," she said.

"King tides in combination with this lowering pressure and high waves can cause coastal flooding."

Marintchenko said the wet weather would start on Saturday, with intermittent showers.

Heavier showers were expected across the Auckland and Northland region on Sunday morning and would turn into heavier, more persistent rain.