A heavy rain watch is in force for the Bay of Plenty this morning.

The MetService is forecasting periods of rain with heavy falls, and possibly thunderstorms for today.

'A low to the west directs a moist and unstable northeasterly flow over the upper North Island,” says a spokesperson for the weather organisation.

'A heavy rain warning remains in force for Northland and the Coromandel Peninsula. Heavy rain watches are in force for eastern parts of Auckland north of Orewa, Great Barrier Island and Bay of Plenty west of Tauranga.

'A moist northerly flow with embedded fronts is expected to bring heavy rain to many areas on Wednesday and Thursday.

'A watch for heavy rain has been issued for Fiordland, Westland south of Otira and the headwaters of the Canterbury and Otago lakes and rivers. Further watches and warnings are likely to be issued closer to the event.

'People are advised to stay up to date with the latest forecasts in case any changes are made.”

A severe weather watch is in force for the region. Image: MetService.

Heavy Rain Warning - Orange

Impact: Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Area: Northland

Period: 7hrs from 8pm Mon, 18 Apr - 3am Tue, 19 Apr

Forecast: Expect a further 40 to 60mm of rain to accumulate on top of the 110 to 150mm that has already accumulated in the east. The heaviest rain is expected in the north and east. Peak rates of 15 to 25mm/h, but 25 to 40mm/h possible in localised thundery downpours. Please note, showers are forecast after this time on Tuesday, with the possibility of localised thundery downpours, but widespread heavy rain is not expected to continue.

Area: Coromandel Peninsula

Period: 19hrs from 8pm Mon, 18 Apr - 3pm Tue, 19 Apr

Forecast: Expect 90 to 120mm of rain. Peak rates of 10 to 25mm/h expected, especially in thunderstorms.

Heavy Rain Watch

Area: Eastern parts of Auckland north of Orewa, also Great Barrier Island

Period: 17hrs from 8pm Mon, 18 Apr - 1pm Tue, 19 Apr

Forecast: Periods of rain, with localised downpours and thunderstorms possible. Rainfall accumulations may approach warning criteria.

Area: Bay Of Plenty west of Tauranga

Period: 23hrs from 8pm Mon, 18 Apr - 7pm Tue, 19 Apr

Forecast: Periods of rain, with heavy falls and thunderstorms possible. Rainfall accumulations may approach warning criteria.

Area: Fiordland, Westland south of Otira and the headwaters of the Canterbury and Otago lakes and rivers.

Period: 36hrs from 11am Wed, 20 Apr - 11pm Thu, 21 Apr

Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria. Note that Warning amounts of rain are considered likely and this Watch will probably be upgraded to a Warning.