Storms kick off week of wild weather

Weather analyst Philip Duncan says conditions are perfect for thunderstorms and heavy showers. Photo / Brett Phibbs

Thunderstorms that hit much of the country yesterday were just the start of a week of wild weather.

A low - affecting an area about the size of Australia - is expected to develop across New Zealand tomorrow bringing thunder and hailstorms, heavy showers and possibly gale-force winds.

Weather Watch head analyst Philip Duncan expects today's weather to be more settled before the large low-pressure system moves in.

The MetService has issued severe weather warnings for some western regions in the North and South Islands and some areas in the east of the South.

Snow across Canterbury and Otago is likely to close alpine roads.

"This is perfect weather for thunderstorms and heavy showers, particularly in the west," Mr Duncan said, but the size of the system might lessen the severity of the storm.

"There is little doubt in my mind that some regions are in for strong winds but a massive low-pressure system like this one doesn't always equate to severe weather. The wider the centre of the low is, the more thinly spread the energy is."

The stormy weather is likely to last a week.

The coldest weather is likely to develop on Saturday or Sunday in the South Island and move into the North Island early next week with strong to gale southwesterlies in coastal areas.

MetService forecaster Cameron Coutts said the top half of the North Island would be the place to be for the warmest temperatures.

Auckland can expect highs of 17C tomorrow, 15C on Saturday and 16C on Sunday. Overnight temperatures on most days will drop to about 9C.

Northland, Waikato, the Bay of Plenty, Gisborne and Hawkes Bay will experience similar temperatures.

South Island temperatures will struggle to reach double digits and the bottom half of the North Island will not be much warmer, with highs of about 11C.

Mr Coutts said the weather was typical for this time of year.

"These patterns can happen at any time, these colder outbreaks. We've just got the right conditions to drag all the air up from the Antarctic so that's going to be a pretty cold sort of spell, like what we're already experiencing. The cold, showery weather is going to continue into early next week."

Rain, hail and thunder brought surface flooding and powercuts to Wellington and Christchurch yesterday as the first of the wild weather hit.

Taranaki also suffered heavy showers and thunderstorms.