MetService is closely monitoring a significant weather shift set to unfold as a large frontal system sweeps northward across the country.

This meteorological event is poised to bring notable changes in temperature, strong winds, and heavy rain over the next 24 hours and into the weekend.

Today, the eastern South Island braces for thunderstorm activity, accompanied by punchy winds and potential hail.

"Rapid changes in weather conditions are expected with this frontal passage," says MetService meteorologist Mmathapelo Makgabutlane.

Thursday boasts warm temperatures in Blenheim (28°C) and Christchurch and Ashburton (27°C).

However, a stark temperature drop is anticipated as the cold front progresses from the South Island to the North Island by Saturday.

Maximum temperatures on Friday in the South Island only reach the low to mid-teens, with Ashburton and Christchurch  at a nippy 12°C and 13°C.

For the North Island, Masterton drops from 25°C on Thursday to 14°C on Saturday, while Auckland and Northland will transition to cooler and fresher air, departing from the "tropical feel" of late.

Brief snowfalls are also possible in elevated areas of the lower South Island late Thursday into Friday.

A significant feature of this weather system is the arrival of strong and blustery southerly winds, affecting the eastern South Island and lower North Island.

A Strong Wind Watch has been issued for Wellington, Marlborough Sounds, and the Kaikōura Coast for Friday from 2 pm to 11 pm.

Makgabutlane advises, "Precautions are recommended, securing loose items and exercising caution on the roads, especially in exposed areas where gusts may approach severe gale."

Strong winds persist over the North Island during the weekend, especially in Gisborne and the Bay of Plenty.

These winds may also generate large waves in the lower North Island on Friday, extending to the eastern North Island on Saturday, with heights reaching 3 to 4 metres.

Extra care is urged for those planning activities near the water during this period.

Lastly, the frontal system also brings rainfall for most of the country.

The wettest conditions are expected to impact the eastern North Island on the back of an already wet start to this past week.

A Heavy Rain Watch is in place for Hawke's Bay and Tairāwhiti/Gisborne from Friday 1 pm to Sunday 9 am.

“This is long period of wet weather, and residents are advised to stay updated with the latest forecasts, as areas may be added or upgraded in the coming days,” Makgabutlane says.

The weather system is expected to move away on Sunday, bringing improved conditions to the South Island and most of the North Island.

The reprieve will be brief, however, as the next low-pressure system approaches in the new week.

Image: MetService.