MetService has issued a Severe Weather Warning for southern and central New Zealand with heavy rain and strong winds expected.

A complex low pressure system is expected to approach New Zealand from the northwest later on Thursday, and then cross the country on Friday and early Saturday. This system is preceded by a strengthening and moist northerly flow, and is followed by unsettled west to northwest winds.

'It's all change for Thursday as the high pressure of the last few days is replaced by an active area of low pressure moving in from the Tasman Sea,” says a MetService spokesperson.

'Severe Weather Warnings have been issued for heavy rain and strong winds across many parts of the South Island for later on Thursday and into Friday.

'A Strong Wind Warning has also been issued for Wellington covering the early hours of Friday morning.”

MetService say the heaviest rain is forecast for the ranges of Westland where 275 to 325 mm of rain could be expected with thunderstorms possible.

Warnings and Watches are in place over southern and central parts of the country for Heavy Rain and Severe Gales. People are advised to keep up to date with the latest forecasts, in case more Watches or Warnings are added.

Heavy Rain Warning - Orange

Impact: Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Area: Tasman west of Motueka

Period: 10hrs from 9pm Thu, 16 Mar - 7am Fri, 17 Mar

Forecast: Expect 70 to 110 mm in the ranges.

Area: Westland

Period: 31hrs from 4pm Thu, 16 Mar - 11pm Fri, 17 Mar

Forecast: Periods of heavy rain. Expect 275 to 325 mm in the ranges and 60 to 100 mm near the coast. Peak rainfall rates of 25 to 35 mm per hour. Thunderstorms possible. Note: Rain expected to ease south of the Glaciers by 6pm Friday, and by 11pm in the north.

Area: Headwaters of the Canterbury lakes and rivers

Period: 31hrs from 4pm Thu, 16 Mar - 11pm Fri, 17 Mar

Forecast: Periods of rain. Expect about 300 mm about the main divide, with 140 to 180 mm within 15 kilometres east of the divide. Peak rainfall rates of 20 to 30 mm per hour. Thunderstorms possible.

Area: Fiordland north of George Sound

Period: 18hrs from 4pm Thu, 16 Mar - 10am Fri, 17 Mar

Forecast: Periods of heavy rain. Expect 100 to 150 mm with peak rainfall rates of 15 to 25 mm per hour. Thunderstorms possible.

Strong Wind Warning - Orange

Impact: Strong wind gusts could damage trees, powerlines and unsecured structures. Driving may be hazardous, especially for high-sided vehicles and motorcycles.

Area: Marlborough and Wellington

Period: 8hrs from 1am - 9am Fri, 17 Mar

Forecast: Severe northerly gales at times in exposed places, gusting 120 km/h. Easing by 6am Friday in Marlborough, and in Wellington by 9am.

Area: Canterbury High Country

Period: 8hrs from 9pm Thu, 16 Mar - 5am Fri, 17 Mar

Forecast: Severe northwest gales at times in exposed places, gusting 120 km/h.

Heavy Rain Watch

Area: Headwaters of the Otago lakes and rivers

Period: 18hrs from 4pm Thu, 16 Mar - 10am Fri, 17 Mar

Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria.

Area: Buller

Period: 12hrs from 7pm Thu, 16 Mar - 7am Fri, 17 Mar

Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria. Thunderstorms possible.

Area: Richmond and Bryant Ranges

Period: 9hrs from 10pm Thu, 16 Mar - 7am Fri, 17 Mar

Forecast: Periods of heavy rain in the ranges. Rainfall amounts may approach warning criteria.

Strong Wind Watch

Area: Buller and Westland

Period: 6hrs from 9pm Thu, 16 Mar - 3am Fri, 17 Mar

Forecast: Northerly winds may approach severe gale at times.

Area: Wairarapa south of Masterton

Period: 8hrs from 1am - 9am Fri, 17 Mar

Forecast: Northwest winds may approach severe gale at times.

Area: Banks Peninsula

Period: 6hrs from 1am - 7am Fri, 17 Mar

Forecast: Northeast winds may approach severe gale at times.

Please keep up with the latest Severe Weather Warnings at MetService.com