Kiwis are being warned to brace for a wet Tuesday, with thunderstorms and flooding possible.

MetService has put several weather watches and warnings in place across the country, with the west of New Zealand expected to feel the brunt of a weather system hovering over the Tasman sea.

reas around Mt Taranaki will see up to 140mm of rain over Tuesday, especially in the afternoon. MetService says that may lead to streams and rivers rising rapidly as well as flooding and slips. It warns residents to be aware of the conditions as it may make driving "hazardous".

There's a similar warning in place for northern parts of Marlborough and Nelson, where up to 150mm of rain is forecast. 

Other parts of the country with heavy rain watches in place include Taranaki, the Bay of Plenty, and most of Canterbury.

WeatherWatch also forecasts the western weather system to cause some trouble on Tuesday. 

"A low pressure system just to the west of the country flings a cold front over the upper South Island and North Island today bringing in some heavy rain, possible thunderstorms for the North Island too.

"Most of the lower South Island is wet also, slowly clearing about Southland from afternoon."

Due to the weather, several Gulf Harbour ferry services will now be run by bus:

Auckland to Gulf Harbour: 7:30am, 9:30am, 10:30am, 12:30pm, 2:45pm, 5:15pm, 5:45pm, 6:45pm & 8:45pm.

Gulf Harbour to Auckland: 7:30am, 8:30am, 10:30am, 11:30am, 1:30pm, 3:45pm, 5:45pm & 7:45pm.

According to WeatherWatch, northern and eastern parts of the North Island will be the warmest, with the eastern North Island expected to hit highs between 24C and 26C. Southland and Otago are only forecast to hit up to 13C.