Taranaki and Waitomo residents are being warned to expect more heavy rain and be alert to possible flooding.

The MetService says downpours of up to 35 millimetres an hour were possible in the Taranaki region before easing in the evening.

It warns of falls of up to 70mm for the region until 6pm with up to 150mm tipped for the higher slopes of Mt Taranaki.

Waitomo can expect falls of up to 30mm an hour and 90mm is expected until 9pm along with thunderstorms.

The forecaster says rivers may rise quickly and the amount of rain has the potential to cause slips and flash floods.

Other areas can also expect to encounter heavy rain but not at the same levels as Taranaki and Waitomo.

An area stretching from Buller in the South Island to the Tararua Range in the North Island will get downpours, as well as Wanganui, south Waikato and eastern Bay of Plenty later in the day.