The MetService has issued a thunderstorm watch for the Bay of Plenty.

A combination of humid subtropical air, and afternoon and early evening wind convergences, are likely to trigger heavy showers and thunderstorms about the central North Island.

Wet and muggy weather is forecast for the Bay of Plenty. Image: MetService.

Areas affected by the watch include Northland, Waikato, Waitomo, Taumarunui, Bay of Plenty, Rotorua, Taupo, Gisborne, Hawke's Bay, Taihape and Wanganui.

'There is a moderate risk of these thunderstorms becoming severe, producing localised downpours and torrential rain of 25 to 40mm/hr and possibly more,” says a statement from the MetService.

'Rainfall of this intensity can cause flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.”

A severe thunderstorm watch means conditions are favourable for severe thunderstorms in and close to the watch area.

People in these areas should be on the lookout for threatening weather conditions and listen for possible severe thunderstorm warnings. Thunderstorm activity should ease later Wednesday evening.

Meanwhile, Tauranga City Council advises that the Mauao base track is closed due to the dangers of a significant swell, combined with an upcoming high tide,

Moturiki Island (Leisure Island) is also being assessed at this stage.

"Significant swell combined with the upcoming high tide are causing waves reaching the base track already, making it potentially unsafe.