A tropical cyclone nearing Australia will hit New Zealand just days before Christmas, forecasters warn.

And the MetService has also issued severe thunderstorm warning today for Waikato, Bay of Plenty, Taupō, Hawke's Bay, Gisborne, and Manawatu, saying the bad weather could develop this afternoon and early evening.

Downpours of between 25mm and 40mm per hour are expected, which could cause surface or flash flooding, and lead to slips and hazardous driving conditions.

MetService duty forecaster Tom Adams said a tropical cyclone, today re-categorised as Category 1, currently hovering over the Gulf of Carpentaria - north of Australia, will eventually hit New Zealand just days before Christmas.

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Tropical Cyclone Owen was forecast to hit here between December 20 and 22.

However, it would be fairly swift and unlikely to still be around when Santa arrived, Adams said.

But that didn't mean Kiwis could bank on a dry Christmas Day.

Adams said it was simply too early to know what the forecast would be for the big day.

Meanwhile, unpredictable showery weather is set to hover over the country for the rest of the week, before the sun is finally expected to put on a show on Sunday.

It means people everywhere other than Southland and Otago should continue to keep an umbrella handy until the weekend.

Northlanders will likely be the unluckiest lot, with a trough from the west due to land on Saturday dropping heavy rain.

Adams said most of the country will continue to experience rain today right through until Friday.

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Given the intermittent nature of showers, it was hard to predict who would be most affected, he said.

However, towns from Hamilton and further north, along with the East Coast, will be looking skyward with trepidation today.

The low will gradually weaken throughout the week, with the weekend currently looking "okay".

Those not affected by showers will continue to experience cloudy yet stable weather.

Your weather
Whangārei: Morning cloud, then increasing fine spells. Chance afternoon shower. Light winds.

High 24C Low 14C

Auckland: Morning cloud, then increasing fine spells. Chance afternoon shower. Sea breezes.

High 23C Low 15C

Hamilton: Cloudy periods with a few morning showers, then becoming fine in the afternoon. Light winds.

High 23C Low 12C

Tauranga: Showers, possibly thundery with hail from afternoon. Light winds.

High 21C Low 15C

Whanganui: Morning cloud and a few showers, then becoming fine. Light winds.

High 21C Low 13C

Napier: Cloudy. A few showers, possibly thundery with hail evening. Light winds.

High 22C Low 14C

Wellington: Morning cloud and a few showers, then becoming fine. Northerlies turning southerly evening.

High 21C Low 13C

Christchurch: Cloudy, with rain or drizzle at times. Easterlies.

High 17C Low 12C

Dunedin: Cloudy with possible morning drizzle, then fine breaks and chance shower. Easterlies.

High 15C Low 12C