MetService is issuing a heavy rain warning for the Bay of Plenty from Ōpōtiki eastwards, with a further 50 to 80mm of rain forecast for later this morning.

The warning includes the Gisborne ranges and East Cape, from 11am to 10pm Monday, October 31.

"Rain is expected to become heavy again later this morning, and a further 50 to 80mm of rain is forecast for the ranges on top of what has already fallen, with lesser amounts elsewhere," says a MetService spokesperson.

"Peak rates of 15 to 25mm/h in the ranges."

Heavy rain and severe gales are also forecast for parts of the South Island from later on Tuesday through to Thursday.

"A front over eastern Bay of Plenty and Gisborne is expected to bring further heavy rain until tonight, and a Heavy Rain Warning remains in place for these areas.

"Another front is forecast to move onto the South Island from the west on Wednesday and should become slow moving over central parts of the Island.

"The front is expected to deliver heavy rain to Westland, northern Fiordland and the Canterbury and Otago headwaters, and possible severe gale north to northwesterlies about the Canterbury High Country, Fiordland, and western parts of Otago and Southland.

"Warnings and Watches for heavy rain and severe gales are now in force for these areas.

"People are advised to keep up to date with the latest forecasts in case any changes are made, or further areas are added."

Other heavy rain warnings:

Area: Westland

Valid: 32 hours from 1:00 am Wednesday to 9:00 am Thursday

Forecast: Expect 200 to 300 mm of rain about the ranges south of Otira, though 300 to 400 mm or possibly more may accumulate on the ranges between Ross and Bruce Bay. Elsewhere, expect 100 to 150 mm of rain to accumulate. Peak rates of 20 to 30 mm/h expected about the ranges from Wednesday morning to Wednesday night, and another period possible on Thursday morning.

Change note 11.14am: The area description has been updated to include all of Westland.

For the latest Tauranga forecast, visit the MetService website.