Thunderstorms are threatening to saturate the country barely a week before Christmas.

The Bay of Plenty, particularly the Eastern Bay, is being warned to expect possible hail.

There is a moderate chance of thunderstorms in the Bay of Plenty this afternoon. Photo: MetService.

'It's like this little blast of winter in the middle of summer,” says MetService meteorologist Emma Blades.

The latest thunderstorm outlook from the MetService says a front should clear western parts of the North Island this evening, while its eastern flank moves onto central New Zealand.

For the upper North Island, the front with the addition of daytime heating should bring heavier showers to many parts.

There is a low risk of isolated thunderstorms this afternoon and evening for the areas from central Hawkes Bay through Taupo to Waikato northwards, as depicted on the charts.

For the Bay of Plenty, also northern Hawke's Bay and Gisborne, the risk of thunderstorms developing is moderate, and they have the potential to bring localised heavy rain of 10 to 25mm/hr and hail 10 to 20mm in diameter, says the MetService.

'Additionally, in this moderate risk area, there is a low risk that severe thunderstorms or convection could produce large hail greater than 20mm in diameter or large accumulations of small or moderate sized hail.”