Scattered heavy showers and thunderstorms could wreak havoc across Auckland, Great Barrier Island and the Coromandel Peninsula this afternoon into early evening.

There is a moderate risk of these thunderstorms becoming severe, producing localised downpours of 25 to 40mm/hr and large hail with diameter in excess of 2cm.

Rain started bucketing down in Waitakere between 1pm and 2pm — accumulating 22.6mm, according to MetService.

MetService meteorologist April Clark said that had eased off now but "there is a lot of heavy rain around" wider Auckland.

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What helps fuel those thunderstorms is a bit of heat at surface level, she said.

Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.

A Severe Thunderstorm Watch remains in force for Auckland, Great Barrier Island and Coromandel Peninsula.

Earlier this morning waterspouts were reported in Auckland's Waitematā Harbour and the Hauraki Gulf as Waiheke Island was battered by a thunderstorm.


Today's weather forecast:
Whangārei

Fine spells and a few showers, possibly heavy with hail until evening. Southwest breezes. 20C high, 11C overnight.

Auckland
Fine spells and isolated showers. Possible thunderstorms and hail until evening. Southwesterlies. 19C high, 12C overnight.

Hamilton
Fine spells, but a shower or two, with possible thunderstorms and hail, mainly this afternoon. Light winds. 19C high, 8C overnight.

Tauranga
A few showers, possibly heavy with hail, easing this evening. Light winds. 20C high, 13C overnight.

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New Plymouth
Fine spells increasing. Chance shower until evening. Southeast breezes. 20C high, 11C overnight.

Napier
Cloudy. A few showers, possibly heavy with hail, clearing afternoon. Easterly breezes. 20C high, 13C overnight.

Whanganui
Fine spells increasing. Chance shower until evening. Southeasterlies. 20C high, 12C overnight.

Wellington
Mostly cloudy, some morning drizzle. Strong southerlies gradually easing. 16C high, 12C overnight.

Nelson
Chance early rain, then becoming fine. Southerlies dying out morning. 20C high, 10C overnight.

Christchurch
Morning low cloud or fog, then fine. Cloud returns at night. Afternoon northeast breezes. 17C high, 7C overnight.

Dunedin
Morning and evening low cloud or fog, otherwise fine. Light winds. 18C high, 11C overnight.