Snow is beginning to ease across parts of the South Island, but the bitter cold is expected to linger.

Police are urging people in Dunedin to avoid unnecessary travel, with snow forcing the closure of several roads, including State Highways 1, 85 and 87.

Emergency services have responded to a number of crashes and reports of vehicles becoming stuck across the city, although no injuries have been reported.

All Dunedin schools have closed for the day, while bus services have also been cancelled.

In Canterbury, State Highway 75 has reopened from Christchurch to Tai Tapu, but remains closed between Duvauchelle and Little River.

MetService meteorologist Braydon White said the cold air was taking longer to reach Christchurch, but temperatures were expected to fall sharply as skies cleared.

“As that rain activity eases off, we get some clearer skies building in behind with high pressure, and that is going to allow the overnight temperature to plummet. We are talking about minus 5 degrees on Thursday morning.”

Wellington is also facing a wintry afternoon, with sleet possible and all Cook Strait ferry services cancelled for the day.