Heavy rain is forecast for Coromandel Peninsula and Gisborne/Tairawhiti overnight, according to the MetService.

"An active front is moving southwards across Coromandel Peninsula and Gisborne/Tairawhiti today and early tomorrow, bringing a period of heavy rain," a MetService spokesperson said.

"Warnings for heavy rain are in force.  People are advised to keep up to date with the latest forecasts."

A Heavy Rain Warning has been issued for Coromandel Peninsula for nine hours from 4pm today until 1am, Wednesday, January 22.

MetService said to expect periods of heavy rain, with a further 40 to 60 mm of rain on top of what has already fallen.

"[There will be] peak intensities of 15 to 25 mm/h until early this evening with possible thunderstorms.

A Heavy Rain Warning has also been issued for Gisborne/Tairawhiti for 16 hours from 4pm today until 8am tomorrow.

"Expect 80 to 100 mm of rain, especially about and north of Gisborne City. Peak intensities of 10 to 15 mm per hour likely, especially this evening and early Wednesday morning."

MetService said there is a minimal chance of the Heavy Rain Warning upgrading to a Red Warning, but streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions are also possible.

"Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously."