Snow is expected to fall on several alpine highways this week as MetService warns of a significant weather change across Canterbury and parts of the South Island, with heavy rain and strong winds also forecast.

After a stretch of warm, dry autumn weather, conditions are set to deteriorate from early Wednesday, prompting warnings for multiple areas.

A heavy rain warning is in place for Banks Peninsula and Canterbury north of Amberley from around 4am Wednesday. Drivers are advised to watch for fast-rising streams and surface flooding, particularly near Lake Forsyth and SH75, the Akaroa highway.

Rain is expected to reach the Kaikōura Coast around midday Wednesday and continue through to early Friday. MetService says high tides and waves may impact SH1, especially near Ōhau Point, from Thursday midday through to Friday midday. Road restrictions or closures are possible.

A heavy rain watch is also in effect for Christchurch and areas south of Amberley.

Snowfall is expected on SH73 between Porters Pass and Arthur’s Pass from 9pm Wednesday through to midday Thursday, with up to 10 to 15 centimetres possible on Porters Pass.

Further inland, sleet and snow are forecast on SH8 over Burkes Pass and SH80 on the Mt Cook/Aoraki highway from Wednesday evening. Ice may form on bridge decks and shaded areas, with snow possible down to road level through Thursday morning.

A strong wind watch is also in place for Buller, Grey and Westland districts, with gusty southwest winds expected from midday Wednesday through to Thursday afternoon.

NZTA is urging drivers to plan ahead, slow down, avoid sudden braking or sharp turns, and drive with headlights on. Motorists should consider avoiding travel during the worst conditions.