It looked like snow in December. But MetService says the whiteout affecting parts of the South Island was caused by severe hail from summer thunderstorms.
MetService forecaster Brian Mercer said the confusion was understandable, with intense hailstorms capable of blanketing the ground even at this time of year. Unlike snow, which forms delicate crystalline flakes, hail is made up of hard balls of ice and typically falls during severe thunderstorms.
Those storms are now driving hazardous conditions on the ground. NZ Transport Agency Waka Kotahi is urging road users and holidaymakers to take extra care as a cold, unstable air mass moves across the island.
NZ Transport Agency Waka Kotahi is urging road users and holidaymakers to take extra care, as a cold and unstable air mass moves across the island.
Large areas of the South Island are being warned to expect potentially severe thunderstorms this afternoon.
Hail has temporarily blocked State Highway 8 between Timaru and Fairlie, with reports of cars becoming flooded. Road crews have been dispatched to the area.
Surface flooding has also been reported further south.
Severe thunderstorm warnings are in place this afternoon for Christchurch and the Selwyn, Ashburton, Timaru and Mackenzie districts.
A lesser severe thunderstorm watch extends down into North Otago, Central Otago, Southern Lakes, Dunedin, Clutha, Southland, Fiordland until 9pm this evening.
As of 2.50pm, severe thunderstorm warnings were issued for Selwyn, Ashburton, Christchurch City, Banks Peninsula, Timaru, and Mackenzie.
These warnings are expected to bring lightning, heavy downpours, and large hail across the affected areas.
A severe thunderstorm warning had been in place for Timaru and Waimate but has since been lifted.
A severe thunderstorm watch remains in place from Christchurch southwards through Canterbury, Otago, Southland and Fiordland from 3pm to 9pm, with MetService warning some storms could turn severe.
MetService meteorologist Katie Lyons said the set-up was a “classic summer pattern”, with daytime heating combining with moisture in the air to trigger afternoon and evening storms.
“As temperatures climb through the afternoon, that gives the atmosphere the buoyancy it needs,” Lyons said.
🟡⚡Severe Thunderstorm Watch Issued⚡🟡
— MetService NZ (@MetService) December 26, 2025
📍Where: Canterbury to Southland and Fiordland
🕛When: 3pm-9pm Saturday 27th
⁉️What: Possible downpours, large hail and lightning strikes. Surface flooding, hazardous driving conditions, and damage from large hail.
Get the full Watch… pic.twitter.com/Oy18NVk5C6
Some storms could bring localised downpours of 25mm to 40mm an hour and hail larger than 20mm, along with the risk of surface flooding and hazardous driving conditions.
“With those heavier downpours there’s a risk of surface flooding, and large hail can also make driving dangerous, which is something to be mindful of with people travelling for the holidays,” Lyons said.
Christchurch was fine this morning, but Lyons said conditions would become increasingly unpredictable later in the day, with heavy showers and thunderstorms possible.
Granity, near Westport on the West Coast, has already experienced a hailstorm this morning with balls of ice covering the ground.
Across the rest of the country, showers are scattered through many regions, with some possibly becoming heavy at times.
There is also a risk of thunderstorms in parts of the lower North Island, including southern Taranaki, Manawatū, Whanganui, northern Wairarapa and southern Hawke’s Bay.
For the main centres this evening, Auckland is expected to remain mostly overcast with occasional showers, Wellington is sunny but windy, and Christchurch faces the sharpest change as storms develop later today.
Looking ahead, attention turns to the North Island early next week, with heavy rain watches already in force for the Coromandel Peninsula and Gisborne/Tairāwhiti from Monday into Tuesday.
Lyons said an active system moving down from the north could bring prolonged heavy rain, particularly for northern and eastern areas.
“It’s lingering longer than we’d like, which means rainfall totals could really start to climb,” she said.
MetService is urging people in affected areas to stay up to date with forecasts and warnings as conditions evolve.