Torrential rain causes flooding in Wellington

Torrential rain has drenched the capital. Photo / NZ Herald

One side of the country has had lovely weather for ducks lately but the other urgently needs more rain to stop drought this winter, a weather forecaster says.

A "one in 30 year event" hit Wellington today, with flooding from Khandallah to Kilbirnie proving too much for the city's drainage network to handle.

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A small tornado also tore through the Taranaki town of Urenui today, while further south, hail pelted poncho-clad students at Canterbury University, some of whom had waited for up to two hours for a glimpse of visiting Prince Harry.

Wellington City Council said today's massive morning downpour created huge stormwater volumes.

The council said rain gauges showed today's dumping was on a scale seen on an average of just once every 30 years - although the council called a downpour a fortnight ago a "one in 80 year" event.

WeatherWatch head analyst Philip Duncan said the west coast of New Zealand had "too much rain" lately, in contrast to the thirsty east side.

A big low pressure system in the Southern Ocean was causing the wet, sometimes windy weather.

Mr Duncan said most western areas had above-average rainfall lately.

"It's not a problem, but it will be if it keeps doing this," he told NZME. News Service.

MetService warned more heavy rain on the South Island's West Coast was likely tomorrow with "significant spillover" and severe northwest gales predicted for the neighbouring Canterbury high country.

Auckland escaped lightly today, at least compared to some earlier forecasts warning of thunderstorms.

"It turned out that the thunderstorms really didn't make it it into the Auckland area," Mr Duncan said.

An area of mixed cold and warm air - a big component in autumn thunderstorm creation - lay just further south, so Auckland was on the fringe of the thunderstorm risk zone today.

WeatherWatch said another burst of heavy showers,with a chance of thunder, would return to Auckland late on Thursday.

The sprawling low pressure system should bring some relief to parched farms in the east, Mr Duncan said.

"The good news about a big low like this that's taking days to cross the country is that while the west coast gets hammered by all the rain, the east coast does get some of the spillover - and I think they're likely to get a little more as the week goes on," he said.

"It should be enough to give them a helping hand."

He said drought-stricken regions needed not only rain, but warmth for grass to grow.

Mr Duncan said the west should get some relief from downpours next week but a dry spell was the last thing many in the east needed now.

"They've got about another month before that time has completely run out. So we're hoping there'll be some positive [signs] for farmers this month."