Bay of Plenty is expected to have the heaviest rain in the North Island today.

Metservice have released information saying that Mount Taranaki, Rotorua, and the Bay of Plenty will accumulate 100 to 130mm of rain, before moving away to the east on Monday.

This amount of rain will cause rivers and streams to rise rapidly, and may lead to slips and surface flooding.

Heavy rain has also fallen in Westland, the Canterbury Headwaters, Buller, Nelson, the Bryant and Richmond Ranges, and should continue through to late this afternoon or tonight.

A complex low pressure system and its associated fronts over the Tasman Sea will affect much of the country today and tomorrow.