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.
Hail stones following a brief storm in Granity, Westport this morning. Photo / Chris Weissenborn
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.