Gale-force winds generating thunderstorms and maybe tornadoes are predicted to bash the region today.

MetService says the coming weather will be "severe" - and the outlook for the weekend isn't much better. Forecasters said a very active front should move quickly across the country today and that's a weather system the experts say is fertile ground for thunderstorms.

They're expecting the stormy weather to affect an area from Waikato to the Kapiti Coast, including western Taihape, and on to the top and west of the South Island.

Gusts, described as "potentially damaging" are expected to reach at least 70km/h over the Whanganui district.


MetService spokesman Gerard Barrow said there was the potential for squally thunderstorms with gusts greater than 110km/h, brief downpours dumping between 25mm and 35mm of rain every hour, and the possibility of a tornado.

"Wind gusts greater than 110km/h can cause some structural damage, including trees and power lines, and may make driving hazardous.

"If any tornadoes occur, they will only affect very localised areas," Mr Barrow said.

He said downpours of this intensity could also cause flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and might lead to slips. "Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."

MetService said northwest gales could become severe for a time from this morning through to late this afternoon.

And it doesn't stop there, with a trough forecast to blast through on Friday, bringing rain to most of the country and more heavy falls in western areas.

The heavy rain could continue into Saturday. Also around this time, a strong westerly flow is likely to spread across the central and upper North Island, with the possibility of severe westerly gales for all regions from Manawatu northwards.

Whanganui's extended period of unseasonally warm and settled weather came to an end on Monday night, when a front blasted through just after 5pm. Winds reached speeds of up to 78km/h, and 7.8mm of rain fell between 5pm and midnight.

However, Whanganui Fire Service said they had received no weather-related call-outs.

A couple of local plumbing firms said they received a few calls from clients about leaves blocking drains during the heavy downpour.