Heavy snow and fallen trees forced the closure of several major highways across the South Island on Monday night, as emergency services responded to vehicles trapped in severe conditions.

State Highway 1, from Dunedin to Palmerston, was closed after the closure zone was extended north from Dunedin to Waitati. State Highway 82 between Waimate and Kurow was also closed because of fallen trees, along with State Highway 79 between Geraldine and Fairlie.

The closures form part of a widespread weather event affecting large parts of the South Island.

Other state highways currently closed include:

• State Highway 80 from Aoraki Mount Cook to Lake Pukaki

• State Highway 8 from Lake Tekapo to Twizel

• State Highway 8 from Lake Tekapo to Fairlie

• State Highway 6 between Haast and Makarora, including Haast Pass

• State Highway 82 from Waimate to Kurow

• State Highway 79 between Geraldine and Fairlie

• State Highway 8 from Tarras to Omarama, including Lindis Pass

• State Highway 83 between Omarama and Kurow

• State Highway 1 from Dunedin to Palmerston

• State Highway 87 from Kyeburn to Mosgiel

• State Highway 94, Milford Sound Highway, between East Gate (Hollyford) and Donne River (Westgate)

Authorities said emergency services were dealing with several vehicles trapped in snow on closed roads. Other highways across the island, while still open, had warnings in place due to heavy snow, fallen trees, or flooding.

Motorists were urged to delay travel or avoid affected routes until conditions improve.