Heavy rain is battering the Taranaki region on Waitangi Day, with one weather station recording a month's worth of rain in just four hours. 

The rainfall, which followed flooding on the South Island's West Coast earlier in the week, has closed roads, downed trees and caused slips. 

Metservice issued a "red" weather warning in place for the region today, saying up to 100mm of rain was expected in the morning and early afternoon. 

This afternoon, Metservice reported that 138mm of rain had been recorded at Cape Egmont between 6am and 10am. 

"This is truly exceptional rainfall for a station at sea level," Metservice said on Twitter. 

"For some perspective, this is the same amount of rainfall that New Plymouth would experience in a typical July across the entire month." 

Footage filmed by residents in Rahotu, 50km south of New Plymouth, showed fast-moving water racing down a flooded street. 

One resident said the town hall had flooded and sewage and fuel could be smelt in the streets. 

Taranaki Civil Defence said that while the Metservice's weather warning was being lifted at 2pm, heavy rain was continuing this afternoon. 

It said State Highway 45 between Okato and Opunake remained closed, and a detour was in place. Motorists were advised only to travel if necessary, and not to drive through floodwaters. 

Civil Defence also said it had received reports of slips on SH3 at Mount Messenger and south of Hawera, though these roads remained open. 

Rivers were flowing at high levels and people in the region were warned to keep away. 

There are also heavy rain warnings in place for the Hawkes Bay north of Napier and Gisborne, and the Tararua Ranges. 

Severe flooding in Taranaki. Video / Supplied