South Island on Alert: MetService Issues Severe Thunderstorm Watch

By Lions Roar News Weather Desk

CHRISTCHURCH, NEW ZEALAND (December 27, 2025) – The holiday reprieve from wild weather is coming to an abrupt end for much of the South Island today. MetService has officially issued a Severe Thunderstorm Watch as a cold and unstable air mass sweeps across the region, bringing the threat of flash flooding and damaging hail.

The watch is in effect from 3:00 p.m. this afternoon until 9:00 p.m. tonight, covering a vast area of the island.

⚡ Key Regions Under Watch

The unstable weather is expected to peak during the afternoon and evening hours. Residents in the following areas should be prepared for sudden changes:

• Canterbury: Including Christchurch, the Canterbury Plains, and the High Country.
• Otago: North Otago, Central Otago, and Dunedin.
• Southern Regions: Southland, Clutha, and the Southern Lakes.
• West Coast: Fiordland, Westland, and Buller.

🌩️ Potential Impacts: Hail and Flooding

MetService warns that these thunderstorms could be “intense and localized,” meaning weather conditions can vary drastically over short distances.

• Large Hail: There is a risk of hail exceeding 20mm in diameter, which can damage crops and property.
• Heavy Downpours: Rainfall intensities of 25mm to 40mm per hour are possible. This level of rain can lead to surface or flash flooding, particularly in low-lying areas or near small streams.
• Dangerous Driving: Motorists on State Highway 1 and mountain passes are urged to exercise caution as visibility may drop to near-zero during heavy rain and hail bursts.

🌦️ Looking Ahead to New Year’s

While the South Island faces a “hairy” Saturday, there is a silver lining for the upcoming week. Forecasters suggest that the South Island may actually be the “best bet” for New Year’s Eve celebrations.

While the North Island is expected to grapple with a new low-pressure system bringing rain to Auckland and Wellington on the 31st, the South Island is predicted to see clearing skies—though temperatures will remain significantly cooler than average for late December.