Tairāwhiti Civil Defence is urging residents to be ready for potential surface flooding, slips and more as heavy rain moves in.

An orange heavy rain warning is in effect for Gisborne/Tai Rāwhiti, north of Tolaga Bay, until 8pm on Friday night.

Between 90 and 120mm of rain is expected, with potential peak rates of up to 20mm per hour.

The public are being told to clear gutters and drains, steer clear of low-lying areas while the heaviest rain comes through, and drive to the conditions.

A heavy rain watch is also in effect for Bay of Plenty, in and around Kawerau. Periods of heavy rain are possible through to 9am on Friday.

"Amounts may approach warning criteria with localised downpours possible," MetService said on Thursday night.

The wet weather is expected to continue through to Sunday.