UPDATED 10.06AM: A severe weather watch in force for the Bay of Plenty is now being upgraded to a warning.

The MetService is predicting heavy rain for 23 horus from 9am today until 8am tomorrow.

"Expect 100 to 130mm of rain. Peak intensities of 20 to30mm/h later this morning and early afternoon, then again overnight tonight with possible thunderstorms," says the weather organisation.

"A front is expected to move over the upper North Island during today, bringing brief heavy northeasterly rain to northern areas.

"A complex low is then forecast to move onto the North Island on Sunday bringing the risk of heavy easterly rain to eastern regions of the North Island and upper South Island."

Image: MetService.

EARLIER:

A severe weather watch for heavy rain is in place for the Bay of Plenty.

For the last couple of days, weather organisations have been predicted heavy rain for both today and tomorrow.

The MetService says a front is expected to move over the upper North Island during today, bringing brief heavy northeasterly rain to northern areas.

"A complex low is then forecast to move onto the North Island on Sunday bringing the risk of heavy easterly rain to eastern regions of the North Island and upper South Island.

"Please keep up to date with the latest forecasts in case any Watches are upgraded to a Warning or further areas are added."

Heavy Rain Watch

Area: The north and east of Northland
Valid: 8 hours from 10pm Friday to 6am Saturday
Forecast: Periods of heavy rain with possible thunderstorms. Rainfall accumulations may approach warning amounts. Note, another period of heavy rain is likely Saturday evening to early Sunday morning.

Area: Coromandel Peninsula
Valid: 9 hours from 5am to 2pm Saturday
Forecast: Periods of heavy rain with possible thunderstorms. Rainfall accumulations may approach warning amounts. Note, another period of heavy rain is likely Sunday morning.

Area: Bay of Plenty
Valid: 24 hours from 11am Saturday to 11am Sunday
Forecast: Periods of heavy rain. Rainfall accumulations may approach warning amounts.

Area: Gisborne north of Tolaga Bay
Valid: 19 hours from 5pm Saturday to 12pm Sunday
Forecast: Periods of heavy rain. Rainfall accumulations may approach warning amounts.

Area: The southern and central ranges of Hawke's Bay, and the coastal hills south of Napier
Valid: 12 hours from 9am to 9pm Sunday
Forecast: Periods of heavy rain. Rainfall accumulations may approach warning amounts. Further heavy rain possible Monday morning.

Area: Wairarapa, including the Tararua District
Valid: 11 hours from 1pm Sunday to 12am Monday
Forecast: Periods of heavy rain. Rainfall accumulations may approach warning amounts, mostly about the hills and ranges. Further heavy rain possible on Monday.

Area: Kaikoura Coast and ranges
Valid: 15 hours from 9am Sunday to 12am Monday
Forecast: Periods of heavy rain. Rainfall accumulations may approach warning amounts. Further heavy rain possible on Monday.