A "bone-chilling" weekend is in store for northern New Zealand, MetService warns, as parts of the North Island cope with flooding and rising rivers today.
The forecaster said a low lingering over the north through Saturday and a very cold southerly outbreak on Sunday would make for a classic wintry weekend.
"Sunday in particular will feel bone-chilling, with strong or gale force winds in many places, rapidly rising seas, rain, and snow to low-ish levels," said MetService meteorologist Daniel Corbett.
"The plummeting snow level on Sunday could make travel over many higher routes challenging."
Heavy rain over the eastern North Island this week has caused the Manawatu River to rapidly rise.
The Moutoa floodgates were opened at 10am today this morning to relieve the river, enabling water to be directed through a shortcut called the Moutoa floodway, protecting downstream areas from major flooding.
Horizons Regional Council group manager operations Allan Cook said the gates, which effectively acted like a giant tap, were opened slowly to keep the river at its target level.
"We are expecting a peak flow of around 1380 cumecs [cubic metres per second] which is towards the lower side of historic opening flows."
Farmers in the floodway were asked to keep stock out of affected area until further notice.
Police said surface flooding had caused the closure of State Highway 56 at Opiki near Palmerston North and detours were in place.
A severe rain warning has been issued for the Kaikoura region, where between 100mm and 125mm may accumulate in the next 18 hours, MetService said.
The storm-battered rail line between Wellington and the Hutt Valley has been closed for urgent repairs this morning, resulting in the cancellation of all off-peak train services.
KiwiRail said inspections had identified minor damage to the sea wall along the Ngauranga-Petone section of the rail line as a result of southerly swells and stormy weather since Wednesday.
The damage comes after the line was closed for a week following last month's massive storm, which also battered the sea wall.
KiwiRail said it had decided to repair two small areas of damage immediately, before the weather deteriorated further.
The repairs would be carried out between 9am until 3pm today to take advantage of the low tide.
Off-peak trains on the Wairarapa and Hutt Valley lines would be replaced by buses from Petone to Wellington while the repairs were carried out. The Melling service would be replaced by buses entirely.
Trains were expected to resume operating from 3pm.
The Desert Rd from Waiouru To Rangipo also remained closed this morning due to heavy snow this week.
The New Zealand Transport Agency advised motorists to instead use SH49 (Waiouru To Raetihi), SH4 (Raetihi To National Park) and SH47 (National Park To Turangi).
Queenstown Lakes District Council advised motorists to take extreme care due to hard frosts in the central South Island this morning and ice in shady areas.
MetService said snow flurries were expected to develop around the summit of Lewis Pass this morning then clear early Saturday.
Between 2cm and 5cm was expected to accumulate on the summit with lesser amounts to 700m.
On a brighter note, Metservice said weather in the first week of the school holidays would gradually improve, becoming drier and warmer by the end of Tuesday.