A severe thunderstorm watch has been issued for the Bay of Plenty.

Unstable, humid conditions over central and northeastern parts of North Island are expected to produce scattered thunderstorms this afternoon and early evening.

For Bay of Plenty, Rotorua, northern Taupo and the ranges of northern Hawkes Bay and Gisborne, there is a risk that some of these thunderstorms could become severe, producing localised downpours with intensities of 25 to 40mm per hour, says 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.

"MetService will continue to monitor the situation closely for severe thunderstorm development and will issue further updates."

This watch affects people in the following weather forecast districts:

Bay of Plenty

Rotorua

Taupo

Gisborne

Hawke's Bay