More rain is being forecast for the Coromandel and Bay of Plenty areas, with a severe weather warning still in force.

The MetService says a humid northerly flow has set up over the country and is here for the long run.

'It is going to be a very wet start to Auckland Anniversary weekend. Heavy rain could cause flooding and slips and make travel hazardous so if you're planning on heading away for the long weekend it's a good idea to keep up with the forecasts and perhaps consider delaying your travel,” says MetService Meteorologist Jessie Owen.

Heavy rain is expected to move onto Northland on Thursday evening where a Heavy Rain Warning is in force until Friday evening.

It will then continue to spread south; a Heavy Rain Watch is in force for northern Auckland on Friday and Heavy Rain Warnings have been issued for the Coromandel and Bay of Plenty from Friday through to Saturday.

There is also a Strong Wind Watch in place for northeasterly winds in Auckland on Friday.

Further south, those celebrating Nelson Anniversary should have better luck, while they may still see some scattered rain or showers across the weekend plenty of fine breaks are also in store.

Hot temperatures across the South Island will take a brief plunge on Saturday after a cold front spreads up the east coast, before bouncing back again on Sunday.

'Christchurch in particular is forecast to drop from a high of 28°C on Friday right down to 21°C on Saturday, before climbing back to a high of 29°C by Monday.”

The humid air from the north is expected to persist into next week, which could bring further bouts of heavy rain to northern areas, and also to the west of the South Island which has largely escaped the heavy rain so far this year.

Image: MetService.